A new classified U.S. intelligence assessment concludes that Iran's leaders are locked in an increasingly heated debate over whether to move further toward developing nuclear weapons, saying the bite of international sanctions may be sowing discord.
The new national intelligence estimate, or NIE, says Tehran likely has resumed work on nuclear-weapons research in addition to expanding its program to enrich uranium—updating a contested 2007 estimate that concluded the arms program had all but halted in 2003.
But it doesn't conclude that Iran has relaunched a full-blown program to try to build bombs. According to the assessment, Iran's debate over whether to do so suggests international sanctions may be causing divisions in Tehran, U.S. officials said. . . .
The NIE's findings suggest that, in the U.S. view, at least some Iranian leaders are worried that economic turmoil fueled in part by international sanctions could spur opposition to the regime—though officials acknowledge it is impossible for outsiders to determine the precise effect of sanctions on decision-making in Tehran.
Iran's government has also taken steps to stifle any possible unrest in response to its own economic measures, after Tehran significantly cut subsidies for fuel, electricity and basic food items in late December.
An NIE is considered the consensus view of all the various U.S. intelligence agencies, and, as a result, carries more weight than an analysis coming from any one part of the intelligence community.
The new assessment is the first full, new analysis by the intelligence community since the 2007 estimate, which concluded that Iran had halted its nuclear-weapon design and weaponization work, as well as its covert uranium enrichment-related activities. Those findings were disputed by some European spy agencies. Iran denies it is trying to develop nuclear weapons.
U.S. officials say at least some of those 2007 assertions have been revised in the new NIE. But the new assessment stops short of rejecting the earlier findings.
"The bottom line is that the intelligence community has concluded that there's an intense debate inside the Iranian regime on the question of whether or not to move toward a nuclear bomb," a U.S. official said. "There's a strong sense that a number of Iranian regime officials know that the sanctions are having a serious effect."
Such conclusions are likely to stiffen the resolve of Obama administration officials to tighten sanctions further. The White House declined to comment on the new intelligence assessment. . . .
The new intelligence findings also reflect a growing consensus among the U.S. and its allies that Tehran's suspected effort to obtain a warhead has been significantly slowed by the combination of sanctions and problems at its nuclear facilities.
Senior Israeli officials said last month that Tehran may be at least four years away from being able to produce a nuclear weapon because of technological difficulties, a notably longer timeline than Israelis had used previously. Soon after, U.S. Secretary of State Hillary Clinton said Washington believed Iran's nuclear program faced mounting "technical" problems.
In a separate threat assessment presented to the Senate Intelligence Committee Wednesday, the director of national intelligence, James Clapper, said the U.S. believes Iran should be capable of producing enough highly enriched uranium for a weapon "in the next few years," provided Tehran makes the decision to do so.
Officials in the U.S., Europe and Asia credit, in part, an international campaign that they say has restricted Iran's ability to procure the raw materials needed to build an atomic bomb.
Officials say Iran has had difficulty acquiring carbon fiber and a particular high-strength steel, two critical components for making machinery used in producing enriched uranium.
Iran's nuclear program also appears to have been slowed by problems in the computer system used to run its enrichment equipment, officials said.
Officials say Tehran is encountering problems deploying advanced centrifuge machines that could drastically accelerate the production of highly enriched uranium, which is needed for a nuclear bomb.
Experts attribute equipment failures among such machines at Iran's main uranium-enrichment plant to a computer worm known as Stuxnet. Iran has acknowledged the computer attacks. Experts speculate that Stuxnet was developed by Israel or the U.S., or both, though neither government has confirmed any role.
A report issued on Wednesday by David Albright, an expert on Iran's nuclear program who heads the Institute for Science and International Security, said it is increasingly accepted that a successful Stuxnet attack in late 2009 or early 2010 destroyed about 1,000 Iranian centrifuges out of about 9,000 at the site.
"The effect of this attack was significant," Mr. Albright said in the report. "It rattled the Iranians, who were unlikely to know what caused the breakage, delayed the expected expansion of the plant, and further consumed a limited supply of centrifuges to replace those destroyed."
Mr. Clapper, in testimony to Congress, said the intelligence community believes Iran is "keeping open the option to develop nuclear weapons in part by developing various nuclear capabilities that better position it to produce such weapons, should it choose to do so. We do not know, however, if Iran will eventually decide to build nuclear weapons."