Diplomacy in the lead on Iran nuclear issue -- for now

Agreement to open Iran’s hidden nuclear complex to inspection has reduced talk of military action and put diplomacy back on track -- at least for a while. But even as the U.S. tries to build international pressure, emerging details suggest it might already be too late for an armed strike.

Everything about Iran’s newly disclosed site near the holy city of Qom complicates the task for the two most likely attackers, the U.S. and Israel. Iranian officials say that’s precisely why they built the facility on an elite military base, fortified with steel and concrete, and buried under a mountain.

Less than a week after President Obama revealed that the U.S. knew about the site, Iran agreed to open it to inspectors from the International Atomic Energy Agency. In a subsequent visit to Tehran, IAEA Director-General Mohamed ElBaradei said inspectors would visit Oct. 25.

The Obama administration and its allies are concerned that, despite Tehran’s denials, Iran’s atomic program masks an effort to build nuclear weapons. Still, Obama has consistently said he favors engagement over confrontation. In part, that reflects a distaste for preemptive military action. But it’s also a result of concerns over Iranian retaliation, the strain on a U.S. military force still heavily committed in Iraq and Afghanistan, and the possibility that such an attack could close the window on political reform inside Iran.

Despite regarding Iran as an existential threat, Israeli officials have indicated they are willing to give diplomacy a chance. However, Obama insists he won’t rule out any options, and administration officials say they won’t wait forever to find out whether Iran is serious about cooperating.

Military planners in the U.S. and Israel developing contingencies for attacking Iran’s nuclear sites have long struggled with a lack of good intelligence, the number and location of the dispersed sites and the distance their forces would have to travel to reach them. Details emerging about the Qom site make their task more difficult -- if not almost impossible.

Defense Secretary Robert M. Gates has said that any attack could at best delay construction of a bomb, if Iran intends to build one.

A military effort to cripple Iran’s nuclear program would require dozens of missile strikes, not only on major facilities but on research installations and locations where centrifuges and other equipment are manufactured and stored, according to current and former U.S. officials. It might also require the insertion of troops.

“If you’re going to have an effective campaign to go in and throw [Iran’s nuclear program] back years, you’re talking about a massive, massive effort,” said a former senior U.S. intelligence official who was involved in examining such scenarios, and discussed them on condition of anonymity.

The main components of Iran’s nuclear program include a uranium enrichment plant at Natanz, a heavy-water reactor at Arak, a uranium-conversion plant at Esfahan and the newly identified site near Qom.

In the past, U.S. spy agencies have struggled in assessing other nations’ nuclear programs. In Iraq, the United States learned after the 1991 Persian Gulf War that it had missed major signs that Baghdad was pursuing the bomb. Twelve years later, the United States erroneously concluded that the work had resumed, only to discover after the 2003 U.S.-led invasion that that assessment was wrong.

The Obama administration has never spelled out what might prompt a U.S. strike, deliberately leaving diplomatic maneuvering room. Nevertheless, former U.S. officials and experts said there are several possible thresholds.

Leonard Spector, director of the James Martin Center for Nonproliferation Studies in Washington, said the U.S. would almost certainly react “if we observe that they are producing highly enriched uranium or . . . were returning to the design and manufacture of actual weapons.”

Although Iran is already enriching uranium at Natanz, the facility is not configured to deliver bomb-grade material. The IAEA’s ElBaradei said in Tehran this month that there was no “concrete proof” Iran has an ongoing weapons program. U.S. spy agencies believe Iran’s work on designing a nuclear warhead was suspended in 2003, although Israeli and British intelligence officials question that conclusion.

Some experts believe the United States might choose to hold off on any attack until Iran actually tested a nuclear device.

In one scenario, the United States could carry out a single missile strike on the Qom facility alone -- a step that might be easier to defend internationally but would do little to slow Iran’s nuclear work.

If strikes are ordered, the U.S. has a major military advantage. Iran’s air defenses are regarded as rudimentary. Still, the United States would probably use stealth aircraft and employ electronic measures to shut down Iranian radar and surface-to-air missiles.

When Israel attacked a nuclear facility being built in Syria in 2007, the Arab nation’s radar was fed false information, preventing the government in Damascus from learning it was under attack until the first bomb fell.

John Wheeler, a former Air Force official, said the U.S. could use cyber warfare to weaken Iranian defenses, disabling the electrical grid and disrupting radio signals and cellphone towers.

One former Defense official said putting teams of special operations forces, known as SOFs, on the ground would improve the accuracy of bombing. Such a ground force could also place explosives at entrances to hidden bunkers, he said.

“The SOF guys would be safe for a while,” said the official. “They could assure accurate target acquisition.”

U.S. officials are developing an array of warheads designed to plunge into the earth and penetrate layers of concrete before being detonated by a delayed-action fuse.

The largest penetrator in the military’s inventory is the 5,000-pound GBU-28. But much larger munitions, including the 30,000-pound “massive ordnance penetrator,” are in development, although experts said early versions might secretly be available.

The Air Force also has a bomb 30 feet long that weighs more than 21,000 pounds. Although not a penetrating bomb, it could destroy exterior features, such as entrances, and severely damage a structure’s interior.

Strikes employing such munitions would probably be successive, with the initial launches focused on entrances and outer defenses, followed by missiles meant to drill deeper into the center of the target.

Locating the center would be difficult. Satellite images of the Qom compound show tunnel entrances and vents scattered across a mountaintop, but they reveal little of the layout underneath.

“Unless you have good human intelligence, you probably don’t have a good idea where inside the mountain the key target is,” said a former senior U.S. military intelligence official. Partly for that reason, the official said, “it is possible to construct a facility that is simply beyond reach.”

Nuclear warheads could destroy even a deeply buried structure, but are an unthinkable option for Washington.

Beyond the obvious diplomatic fallout, military options carry many other risks.

An attack could weaken the opposition movement disputing President Mahmoud Ahmadinejad’s reelection in June by uniting conservatives and reformers against a national threat.

Or it could give authorities an opportunity to take further action against those seeking more democracy.

If a military strike left even remnants of the program intact, it might well harden Iran’s resolve to acquire the bomb -- even if it hadn’t been pursuing a weapons program before.

U.S. spy agencies have warned that Tehran might retaliate by launching missiles toward Israel; striking U.S. installations in Iraq and Afghanistan; closing off the Strait of Hormuz, a vital route for oil shipments; and carrying out attacks on other continents through the militant group Hezbollah, which it supports.

“The assumption is that they would strike out, unleashing their terrorist clients and using whatever military capabilities they’ve got,” said a former senior U.S. intelligence official familiar with classified assessments. “I don’t think anybody seriously contemplates that they would say, ‘Game over.’ ”

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greg.miller@latimes.com

julian.barnes@latimes.com