Little more than a year after U.S. spy agencies concluded that Iran had halted work on a nuclear weapon, the Obama administration has made it clear that it believes there is no question that Tehran is seeking the bomb.
In his news conference this week, President Obama went so far as to describe Iran's "development of a nuclear weapon" before correcting himself to refer to its "pursuit" of weapons capability.
Obama's nominee to serve as CIA director, Leon E. Panetta, left little doubt about his view last week when he testified on Capitol Hill. "From all the information I've seen," Panetta said, "I think there is no question that they are seeking that capability."
The language reflects the extent to which senior U.S. officials now discount a National Intelligence Estimate issued in November 2007 that was instrumental in derailing U.S. and European efforts to pressure Iran to shut down its nuclear program.
As the administration moves toward talks with Iran, Obama appears to be sending a signal that the United States will not be drawn into a debate over Iran's intent.
"When you're talking about negotiations in Iran, it is dangerous to appear weak or naive," said Joseph Cirincione, a nuclear weapons expert and president of the Ploughshares Fund, an anti-proliferation organization based in Washington.
Cirincione said the unequivocal language also worked to Obama's political advantage. "It guards against criticism from the right that the administration is underestimating Iran," he said.
Iran has long maintained that it aims to generate electricity, not build bombs, with nuclear power. But Western intelligence officials and nuclear experts increasingly view those claims as implausible.
U.S. officials said that although no new evidence had surfaced to undercut the findings of the 2007 estimate, there was growing consensus that it provided a misleading picture and that the country was poised to reach crucial bomb-making milestones this year.
Obama's top intelligence official, Dennis C. Blair, the director of national intelligence, is expected to address mounting concerns over Iran's nuclear program in testimony before the Senate Intelligence Committee today.
When it was issued, the NIE stunned the international community. It declared that U.S. spy agencies judged "with high confidence that in fall 2003, Tehran halted its nuclear weapons program."
U.S. intelligence officials later said the conclusion was based on evidence that Iran had stopped secret efforts to design a nuclear warhead around the time of the U.S. invasion of Iraq.
Often overlooked in the NIE, officials said, was that Iran had not stopped its work on other crucial fronts, including missile design and uranium enrichment. Many experts contend that these are more difficult than building a bomb.
Iran's advances on enrichment have become a growing source of alarm. Since 2004, the country has gone from operating a few dozen centrifuges -- cylindrical machines used to enrich uranium -- to nearly 6,000, weapons experts agree.
By November, Iran had produced an estimated 1,400 pounds of low-enriched uranium, not nearly enough to fuel a nuclear energy reactor, but perilously close to the quantity needed to make a bomb.
A report issued last month by the Institute for Science and International Security concluded that "Iran is moving steadily toward a breakout capability and is expected to reach that milestone during the first half of 2009." That means it would have enough low-enriched uranium to be able to quickly convert it to weapons-grade material.
Tehran's progress has come despite CIA efforts to sabotage shipments of centrifuge components on their way into Iran and entice the country's nuclear scientists to leave.
Iran still faces considerable hurdles. The country touted its launch of a 60-pound satellite into orbit this month. Experts said Iran's rockets would need to be able to carry more than 2,000 pounds to deliver a first-generation nuclear bomb.
And there are indications that the U.S. and Iran are interested in holding serious diplomatic discussions for the first time in three decades. Iranian President Mahmoud Ahmadinejad said this week that his nation was "ready to hold talks based on mutual respect," and Obama indicated that his administration would look for opportunities "in the coming months."
Hassan Qashqavi, spokesman for Iran's Foreign Ministry, on Wednesday warned the U.S. not to wait for Iranian presidential elections this year, because ultimate authority rests with supreme leader Ayatollah Ali Khamenei.
He also said Iran would be patient.
"Since a new administration came to power in the U.S., we do not want to burn the opportunity of President Obama and give him time to change the reality on the ground," Qashqavi said.
But experts said Iran was now close enough to nuclear weapons capability that it may be less susceptible to international pressure.
"They've made more progress in the last five years than in the previous 10," Cirincione said.
Special correspondent Ramin Mostaghim in Tehran contributed to this report.