After more than a decade of working behind layers of front companies and in hidden laboratories, Iran appears to be in the late stages of developing the capacity to build a nuclear bomb.
Iran insists that like many countries it is only building commercial nuclear reactors to generate electricity for homes and factories. "Iran's efforts in the field of nuclear technology are focused on civilian application and nothing else," President Mohammad Khatami said on state television in February. "This is the legitimate right of the Iranian people."
But a three-month investigation by The Times -- drawing on previously secret reports, international officials, independent experts, Iranian exiles and intelligence sources in Europe and the Middle East -- uncovered strong evidence that Iran's commercial program masks a plan to become the world's next nuclear power. The country has been engaged in a pattern of clandestine activity that has concealed weapons work from international inspectors. Technology and scientists from Russia, China, North Korea and Pakistan have propelled Iran's nuclear program much closer to producing a bomb than Iraq ever was.
No one is certain when Iran might produce its first atomic weapon. Some experts said two or three years; others believe the government has probably not given a final go-ahead. But it is clear that Iran is moving purposefully and rapidly toward acquiring the capability.
Among the findings:
* A confidential report prepared by the French government in May concluded that Iran is surprisingly close to having enriched uranium or plutonium for a bomb. The French warned other governments to exercise "the most serious vigilance on their exports to Iran and Iranian front companies," according to a copy of the report provided by a foreign intelligence service.
* Samples of uranium taken by U.N. inspectors in Iran in June tested positive for enrichment levels high enough to be consistent with an attempt to build a nuclear weapon, according to a foreign intelligence officer and an American diplomat. The Reuters news service first reported the possibility that the material was weapons-grade last month.
* Iran is concealing several weapons research laboratories and evidence of past activity at a plant disguised as a watch-making factory in a Tehran suburb. In June, U.N. inspectors were refused access to two large rooms and barred from testing samples at the factory, called the Kalaye Electric Co.
* Tehran secretly imported 1.8 tons of nuclear material from China in 1991 and processed some of it to manufacture uranium metal, which would be of no use in Iran's commercial program but would be integral to weapons production.
* As early as 1989, Pakistani generals offered to sell Iran nuclear weapons technology. Abdul Qadeer Khan, a Pakistani nuclear scientist regarded by the United States as a purveyor of nuclear secrets, has helped Iran for years. "Pakistan's role was bigger from the beginning than we thought," said a Middle Eastern intelligence official.
* North Korean military scientists recently were monitored entering Iranian nuclear facilities. They are assisting in the design of a nuclear warhead, according to people inside Iran and foreign intelligence officials. So many North Koreans are working on nuclear and missile projects in Iran that a resort on the Caspian coast is set aside for their exclusive use.
* Russian scientists, sometimes traveling to Iran under false identities and working without their government's approval, are helping to complete a special reactor that could produce weapons-grade plutonium. Moscow insists that it is providing only commercial technology for the civilian reactor under construction near the Persian Gulf port of Bushehr, an assertion disputed by Washington.
* In recent months, Iran has approached European companies to buy devices that can manipulate large volumes of radioactive material, technology to forge uranium metal and plutonium and switches that could trigger a nuclear weapon. European intelligence sources said Tehran's shopping list was a strong indication that Iran has moved to the late stages of weapons development.
A nuclear-armed Iran would present the United States with a difficult political and military equation. Iran would be the first avowed enemy of Israel to possess a nuclear bomb. It also has been labeled by the Bush administration as a state sponsor of international terrorism.
Iranian nuclear weapons could shift the balance of power in the region, where Washington is trying to establish pro-American governments in Afghanistan and Iraq. Both of those nations border Iran and are places where Tehran wants to exert influence that could conflict with U.S. intentions, particularly in Iraq.
The Bush administration, which partly justified its war against Iraq by stressing concerns that Saddam Hussein had revived his nuclear weapons program, calls a nuclear-armed Iran unacceptable. At his news conference Wednesday, President Bush said he hopes international pressure will convince the Iranians that "development of a nuclear weapon is not in their interests," but he added that "all options remain on the table."
Foreign intelligence officials told The Times that the Central Intelligence Agency, which has long contended that Iran is building a bomb, has briefed them on a contingency plan for U.S. air and missile attacks against Iranian nuclear installations. "It would be foolish not to present the commander in chief with all of the options, including that one," said one of the officials.
A CIA spokeswoman declined to confirm or deny that such a plan has been drafted. "We wouldn't talk about anything like that," she said.
There is precedent for such a strike. Israeli fighter-bombers destroyed a French-built nuclear reactor outside Baghdad in 1981 shortly before it was to go online. The attack set back Iraq's nuclear program and drove it underground.
Taking out Iran's nuclear infrastructure would prove tougher, said Israeli military planners and outside analysts. For one thing, the facilities are spread around the country and small installations are still secret. At least one key facility is being built to withstand conventional airstrikes.
Contacts between Washington and Tehran are very limited, and analysts said U.S. decision-making is still dominated by a distrust of Iran rooted in the taking of American hostages during the Islamic Revolution in 1979 and an ideological aversion to negotiating with a regime regarded as extremist.
"The administration does not have a strategy because there is a fight in the administration over whether you should even deal with this government in Iran," said George Perkovich, a nuclear weapons expert at the Carnegie Endowment for International Peace in Washington.
For now, the Bush administration is pinning much of its hopes of containing Iranian nuclear ambitions on the same international inspection apparatus that it blames for failing to locate weapons of mass destruction in Iraq.
So far, the U.N.-affiliated International Atomic Energy Agency, based here in Vienna, has preferred negotiation to confrontation with Iran.
In a June 16 report to the 35 countries represented on the agency's board, its director-general, Mohamed ElBaradei, criticized Iran for concealing many of its nuclear activities. But he resisted U.S. pressure to declare Iran in violation of the Nuclear Nonproliferation Treaty, which was created in 1968 to stop the spread of nuclear weapons.
Inspections are continuing along with Iranian roadblocks to a thorough examination, according to officials monitoring the progress. Still, IAEA officials hope to have a clearer picture of Iran's nuclear program by Sept. 8, when a follow-up report to the board is due.
The Iranian Foreign Ministry did not respond to telephone requests for interviews or to written questions for this article. Iran said last year that it plans to build six civilian reactors to generate electricity for its fast-growing population of 65 million. Ministry spokesman Hamid Reza Asefi has said that allegations that Iran is concealing a weapons program are "poisonous and disdainful rumors" spread by the United States.
Iran's civilian nuclear energy program started in 1974 and was interrupted by the Islamic Revolution. It got back on track in 1995, when Russia signed an $800-million contract to complete the commercial reactor at Bushehr, which is scheduled to come online next year.
Russia also promised to sell Iran the uranium fuel to power the reactor. But Iran maintains that it wants to develop its own nuclear fuel-making capability, a position that has roused international suspicions.
Typically, nations with civilian nuclear programs buy fuel from the countries that export the reactors because the fuel-making process is complicated and expensive. In the most common way to make the fuel, uranium ore is converted to a gas and pumped into centrifuges, where rotors spinning at twice the speed of sound separate isotopes. The process concentrates, or "enriches," the uranium to the point that fission can be sustained in a reactor, which pumps out heat to drive electrical turbines.
The same enrichment process can concentrate fissionable uranium at greater levels to produce material for a bomb.
Countries that try to enrich their own uranium or manufacture plutonium in special reactors are immediately suspected of trying to join the elite nuclear arms club. Israel, India and Pakistan developed their own plants for producing fissile material for bombs under the guise of commercial reactors.
Iran agreed not to produce nuclear weapons when it signed the Nuclear Nonproliferation Treaty in 1970, which opened the door for it to acquire civilian reactors. The treaty does not prohibit Iran from producing or possessing enriched uranium but requires it to submit its nuclear facilities to international monitoring to ensure that materials are not diverted to weapons use.
Iran has permitted inspections of its declared commercial nuclear facilities. But last year, an Iranian exile group pinpointed a secret underground enrichment plant outside Natanz, a small mountain town about 200 miles south of Tehran known for its bracing climate and fruit orchards.
In December, the Institute for Science and International Security, a small think tank in Washington, published satellite photos of Natanz from the archives of a commercial firm, DigitalGlobe. The photos showed large-scale construction inside the perimeter of a security fence. Among the buildings were a pilot centrifuge plant and two underground halls big enough for tens of thousands of centrifuges, the institute said.
Pressure mounted to allow international monitors into Natanz, and senior IAEA officials visited the plant in February. They found 160 assembled centrifuges and components for 1,000 more. Moreover, the equipment was to be housed in bunkers 75 feet deep, with walls 8 feet thick.
The level of centrifuge development at Natanz already reflects thousands of hours of testing and advanced technological work, experts said. By comparison, Iraq had tested a single centrifuge for about 100 hours when IAEA inspectors began dismantling Baghdad's nuclear weapons program after the 1991 Persian Gulf War.
"They are way ahead of where Iraq was in 1991," said a U.N. official who is familiar with both programs.
Once it is up and running, Natanz could make enough material for a bomb within a year and eventually enough for three to five bombs a year, experts said.
The Iranian exile group also revealed a secret site near Arak, a city of 400,000 in western Iran known as a historic center for weaving fine Persian carpets. Under international pressure, Iran conceded in February that it plans to build a special type of reactor there that will generate plutonium for research. Plutonium is the radioactive material at the heart of some of the most powerful nuclear bombs.
The disclosures cast previous Iranian government statements in a new light.
Hashemi Rafsanjani, head of an influential government council and president of Iran from 1989 to 1997, gave a speech on Dec. 14, 2001, that has been interpreted widely as both a signal that Iran wants nuclear weapons and a threat to use them against Israel. Describing the establishment of the Jewish state as the worst event in history, Rafsanjani warned, "In due time the Islamic world will have a military nuclear device, and then the strategy of the West would reach a dead end, since one bomb is enough to destroy all Israel."
Rafsanjani has since stepped back in his rhetoric, noting in a sermon on Friday that "because of religious and moral beliefs and commitments that the Koran has created for us, we cannot and will not pursue such weapons that destroy humanity."
On July 20, Iran unveiled a missile based on a North Korean design that brings Israel within range and hailed the event as an important step in protecting the Palestinians. Experts said the new missile could be armed with a small nuclear warhead, and Iran is developing a version that will carry a heavier payload.
"Today our people and our armed forces are ready to defend their goals anywhere," Ayatollah Ali Khamenei, Iran's supreme leader, said in a ceremony unveiling the missile.
Many outside experts as well as Iranians say that even reformers linked to Iranian President Khatami believe that Iran needs a deterrent against its nuclear neighbors -- Israel, Russia and Pakistan -- and possibly against the United States.
"These weapons would guarantee the territorial integrity and national security of Iran," Nasser Hadian, a professor at Tehran University who is aligned with the reformers, said in a telephone interview from New York, where he is teaching at Columbia University. "We feel that we cannot possibly rely on the world to provide security for us, and this is felt by all the factions."
At a symposium in Rome in early July, ElBaradei told the audience that stopping the spread of nuclear, chemical and biological weapons depends greatly on eliminating the incentives for states to possess them. "It is instructive that the majority of the suspected efforts to acquire WMD are to be found in the Middle East, a hotbed of instability for over half a century," he said.
A senior U.N. official said he is not sure that Iran is developing a bomb. But the different fates of Iraq and North Korea, the other members of what Bush called the "axis of evil," demonstrate why countries out of favor with the United States might want a nuclear weapon, he added.
Iraq did not have a bomb and was easily invaded, he said, while North Korea claims to have a bomb and is trying to use it as a bargaining chip with the U.S. for security assurances and possibly increased aid. "If a regime has the feeling that it is not on the right wavelength with the United States, its position is to have a nuclear weapon," he said.
Iran faces numerous technological obstacles before it can produce a nuclear bomb, according to intelligence officials and independent experts. Once those problems are solved or close to being solved, some experts said they expect Iran to withdraw from the nonproliferation treaty, as North Korea did, and close its doors to IAEA inspectors.
"They have made the decision to develop a breakout capability, which will give them the option to leave the treaty in the future and complete a nuclear weapon within six months or a year," said Gary Samore, director of nonproliferation programs at London's International Institute for Strategic Studies and a former Clinton administration security official. "I think the program is probably unstoppable through diplomatic means."
"I don't believe they have passed the point of no return," said Perkovich, the nuclear weapons expert at the Carnegie Endowment. "We should try to reverse Iran's direction by providing better, low-cost options to fuel the Bushehr electricity plant and by easing the security concerns that make Iranians, reformers and hard-liners, interested in getting a bomb."
Diplomacy has proved an imperfect solution in the past. The Clinton administration persuaded China not to sell nuclear items to Iran in the mid-1990s. Administration officials later used sanctions and negotiations to convince Russia to curb technology transfers to Iran's civilian program that U.S. intelligence believed were being diverted to weapons work.
But Russia is committed to the Bushehr reactor, which generates 20,000 jobs for its beleaguered nuclear industry. The project also allows hundreds of Iranians to train in Russia, raising concerns within the intelligence community that knowledge and hardware for weapons work will slip through.
Officials in Moscow, outside experts and foreign intelligence officials said economics are driving continuing Russian assistance to the Iranian weapons program and that it is probably occurring without government approval. They said thousands of Russian physicists, mathematicians and other scientists are unemployed or paid a pittance at home, pushing them to sell their expertise elsewhere.
"Russian scientists are freelancing, leading to a leakage of expertise, and you can't control that," said Bobo Lo, a former Australian diplomat and associate fellow at the Royal Institute of International Affairs in London. "That's where it gets really messy with the Iranians."
"Iran has made tremendous progress during the last two years, and according to our estimates it could reach a technical capability to create a nuclear device by 2006," said Anton Khlopkov, a nuclear expert at Moscow's Center for Policy Studies in Russia. "The problem is neither Russia nor the U.S. nor the IAEA had a clear understanding about real Iranian achievements in the nuclear field."
U.S. Secretary of State Colin L. Powell echoed the sentiment in March, saying on a CNN program, "It shows you how a determined nation that has the intent to develop a nuclear weapon can keep that development process secret from inspectors and outsiders, if they really are determined to do it."
Plants as large as Natanz are not necessary to build a bomb. Once the technology is developed, as few as 500 centrifuges can enrich enough uranium for a small weapon, experts said. Hiding that number would be easy, said an IAEA official, which is why intelligence officials are concerned about several smaller, still-secret plants throughout Iran.
For example, officers from two foreign intelligence agencies said weapons research is being conducted at a plant outside Kashan. One of the intelligence officials said the plant was involved in nuclear fuel production in two large halls constructed 25 feet underground.
The National Council of Resistance of Iran, the Paris-based exile group that revealed the Natanz and Arak sites, said in July that it had pinpointed two more weapons research locations in a rural area called Hashtgerd about 25 miles northwest of Tehran. The group is the political arm of the Moujahedeen Khalq, which is listed by the U.S. State Department as a terrorist group, but independent experts said its information from inside Iran has often been accurate. IAEA inspectors' requests to visit the Hashtgerd sites have been refused by Iranian authorities.
This spring, after considerable pressure from the IAEA, Iran reluctantly allowed inspectors to visit a nondescript cluster of two warehouses and smaller buildings tucked into an alley in the Tehran suburb of Ab-Ali. The place, called the Kalaye Electric Co., claimed to be a watch factory, but Iran conceded it had been an assembly point for centrifuges.
When the IAEA team arrived in March, they were refused access to the plant. A second trip in May was slightly more successful -- inspectors entered the buildings, but two large rooms were declared off limits, according to new information from U.N. officials.
On June 7, inspectors returned to Iran for four days of probes at various sites. This time authorities refused to let them near Kalaye, U.N. officials said. They also were barred from using sophisticated testing equipment the team had brought from Vienna.
Such tests could detect a particle of enriched uranium within a huge radius and determine whether its concentration exceeded the 2%-to-5% level generally used in civilian reactor fuel. One IAEA official compared the ability of a swipe to detect enriched particles to finding a four-leaf clover in a field of clover 6 miles long, 9 miles wide and 150 feet deep.
But during their trip in June, IAEA inspectors took samples from an undisclosed location in Iran that tested positive for enriched uranium at a level that could be used in weapons, according to diplomatic and intelligence sources. IAEA officials refused to comment on the report.
Chinese Uranium Ore
Officials from two foreign intelligence services said Iranian scientists used nuclear material from a secret shipment from China to help enrich uranium at Kalaye and elsewhere.
China had long denied rumors about transferring nuclear materials to Iran. Early this year, U.N. officials said in interviews, the Chinese admitted selling Iran 1.8 tons of uranium ore and chemical forms of uranium used in the enrichment process in 1991.
Faced with a letter describing China's admission, Iranian authorities acknowledged receipt of the material, said the officials. At the same time, Iran said some of the chemicals were used at Tehran's Jabr ibn Hayan laboratory to make uranium metal, which has no use in Iran's commercial program but is a key part of a nuclear weapon.
In addition to China and Russia, Pakistan and North Korea have played central roles in Iran's nuclear program, according to foreign intelligence officers and confidential reports prepared by the French government and a Middle Eastern intelligence service.
North Korean technicians worked for years helping Iran develop the Shahab-3 missile, unveiled last month in Tehran. A foreign intelligence official and a former Iranian intelligence officer said the Koreans are now working on a longer-range Shahab-4 and providing assistance on designs for a nuclear warhead.
The foreign intelligence official said high-ranking North Korean military personnel have been seen at some of Iran's nuclear installations. A hotel is reserved for North Koreans in Tehran and a resort on the Caspian Sea coast northwest of Tehran has been set aside for their use, according to one of the sources and a U.N. official.
The centrifuges seen by IAEA officials at Natanz in February were based on a Pakistani design, according to intelligence officials. The design and other new evidence point to Pakistan as a bigger supplier of nuclear weapons technology to Iran than initially thought, said foreign intelligence officers, Iranian exiles and independent experts.
While U.S. intelligence is aware of Pakistan's help to Iran, the Bush administration has not pushed the issue with Islamabad because of Pakistan's role as an ally in the battle against the Al Qaeda terrorist network and Afghanistan's Taliban, outside experts and foreign intelligence officials said.
Signs of Pakistani Aid
The most convincing sign of Pakistan's role in Iran comes from what several people described as the long involvement in Iran of Khan, the scientist regarded as the father of Pakistan's nuclear bomb.
The CIA concluded in a top-secret analysis last year that Khan shared critical technology on centrifuges and weapons-test data with North Korea in the late 1990s. The agency tracked at least 13 visits by Khan to North Korea over a span of several years, according to a January article in the New Yorker magazine.
Two former Iranian officials and American and foreign intelligence officials said Khan travels frequently to Tehran to share his expertise. Most recently, two of these people said, he has worked as a troubleshooter to iron out problems with the centrifuges and with weapons design.
Ali Akbar Omid Mehr, who was in charge of Pakistani affairs at Iran's Foreign Ministry in 1989 and 1990, said he came across Khan as he prepared what is known as a "green book" detailing contacts between Tehran and Islamabad.
"I saw that Mr. A. Q. Khan had been given a villa near the Caspian Sea for his help to Iran," Mehr said in an interview in Denmark, where he and his family live under assumed names since he defected in late 1995.
His account of the villa was supported by other Iranian exiles.
Khan might have played a role in a previously undisclosed offer from Pakistani military commanders to sell nuclear weapons technology to Iran in 1989, two former senior Pakistani officials said in separate interviews describing the episode.
According to their accounts, soon after Rafsanjani's election as president of Iran in 1989, he took Benazir Bhutto, then prime minister of Pakistan, aside at a reception in Tehran and told her about the proposal from her generals.
Rafsanjani was commander of Tehran's armed forces at the end of the Iran-Iraq war in 1988, and one of his goals as president was to reestablish his country as a regional power. He told Bhutto that the Pakistani generals wanted to transfer the technology secretly, on a military-to-military basis, but he wanted her to approve the transaction, the former Pakistani officials said.
Earlier that year, Bhutto had appeared before the U.S. Congress and promised that Pakistan would not export nuclear technology. Bhutto often bucked the generals, and the two officials said she blocked the transfer -- at least until she was ousted in 1996.
Current Pakistani President Pervez Musharraf said in an interview with The Times that his country never provided nuclear assistance to Iran, before or after he took office in a military coup in October 1999. "Zero," the general insisted. "Never worked -- even before -- never worked with Iran. This is the first time this has been raised, ever."
Pressured by the United States, Musharraf removed Khan as head of Pakistan's nuclear program nearly two years ago. Since then, Musharraf said, Khan has been retired and his travel is not monitored.
Other intelligence officials and governments disputed Musharraf's denial.
"There are convincing indications about the origin of the technology -- it is of Pakistani type -- but Iran undoubtedly controls the manufacturing process of centrifuges and seems even able to improve it," said the French government report on Iran's nuclear program, which was delivered in May to the Nuclear Suppliers Group, an organization of governments with nuclear programs.
A growing body of evidence suggests that Iran is simultaneously pursuing another way to produce material for a bomb.
This alternative is a heavy-water reactor, which could breed weapons-grade plutonium. In the initial stage of the program, Iran is building a plant to distill heavy water near the Qareh Chay River, about 35 miles from Arak. Heavy water, which is processed to contain elevated concentrations of deuterium, allows the reactor to operate with natural uranium as its fuel and produce plutonium.
This type of reactor is used in some places to generate electricity, but it is better known as a means of producing plutonium for weapons that bypasses uranium enrichment and its many technical obstacles. As a result, the presence of a heavy-water reactor is often regarded as a sign that a country is trying to develop a weapon.
American spy satellites had detected construction at Natanz before its existence was made public last year. But the work near Arak had remained secret because the plant under construction looked like any other distillery or similar factory, according to intelligence officials and U.N. authorities.
After exiles revealed Arak's existence, Gholamreza Aghazadeh, the president of Iran's atomic energy organization, informed the IAEA that the planned reactor was strictly meant for research and producing radioisotopes for medical use.
To many experts, however, the project raises another red flag. "For Iran, there is no justification whatsoever to have a heavy-water plant," said Samore of the International Institute for Strategic Studies.
Echoing him, a senior U.N. official said, "The heavy-water plant sticks out like a sore thumb."
Iran first tried to buy heavy-water reactors as turnkey projects from China and India in the mid-1990s, according to a previously undisclosed dossier prepared by a foreign intelligence agency and provided to The Times. Blocked on that front by the United States, according to former U.S. officials, Iran decided to build its own and turned to two Russian institutes.
The United States learned of the cooperation through telephone intercepts and imposed sanctions on the Russian institutes in 1999. The sanctions remain in effect, but officials with foreign intelligence agencies and the CIA said there is evidence that Russian scientists are still providing expertise for the project.
Khlopkov, the Russian nuclear expert, said he thinks it is unlikely that Russian scientists are helping Iran with any of its weapons programs. Still, he said, the recent disclosures about the Iranian program surprised Moscow and might cause Russia to cancel a second planned reactor unless Iran agrees to stricter international inspections of its nuclear facilities.
Despite Iran's progress, most experts said it is unlikely to develop a weapon without more outside help, particularly in procuring specialty technology. That is why some said they were alarmed by Iran's recent attempts to buy critical dual-use technology, which has military and civilian applications.
In November, German authorities blocked an attempt by businessmen allegedly working on behalf of Iran to acquire high-voltage switches that could be used for both breaking up kidney stones and triggering a nuclear weapon.
French authorities reported that French firms with nuclear expertise have received a rising number of inquiries from suspected Iranian front companies for goods with military uses.
In a previously undisclosed incident, French authorities recently stopped a French company from selling 28 specialized remote manipulators for nuclear facilities to a company in Dubai, United Arab Emirates, that the authorities said was a front for Iran's nuclear program.
Because the manipulators were designed to handle heavy volumes of radioactive material, intelligence authorities suspected they were destined for a plant in which uranium or plutonium would be reprocessed on a large scale.
"Such intent is indicative of a willingness to move from a laboratory scale to an industrial scale," said a European intelligence official who is familiar with details of the attempt.
The pattern of attempted purchases and the discovery of previously secret nuclear installations led the French government to conclude in May that Iran is using its civilian nuclear program to conceal a military program.
"Iran appears ready to develop nuclear weapons within a few years," said the French report to the Nuclear Suppliers Group.