WASHINGTON—U.S. officials are concerned that Iran may be closer than they previously believed to mastering the process for producing fuel for a nuclear weapon.
Their unease stems from a recent briefing at which U.N. International Atomic Energy Agency experts reported that Iran was close to operating a test network of 164 machines, called centrifuges, that spin uranium hexafluoride gas into enriched uranium, U.S. officials and a foreign diplomat said.
Depending on its duration, the process produces low enriched uranium for power plants and highly enriched uranium for nuclear weapons.
The report came amid a deadlock in two-week-old talks among the United States, Britain, France, Russia and China—the U.N. Security Council permanent members—on how to deal with Iran's nuclear program.
The IAEA and several European nations disputed the Bush administration's charges about Iraq's nuclear weapons program, but there's wider international agreement about Iran's nuclear efforts.
Should Iran quickly overcome the numerous technical obstacles to operating the test network, known as a cascade, it could accelerate the installation of an industrial-scale plant and begin producing highly enriched uranium much sooner than currently forecast, the U.S. officials and the diplomat said. They spoke on condition of anonymity because they weren't authorized to discuss the issue.
Based on the IAEA data, U.S. experts have concluded that "Iran could be as little as two to three years away from having nuclear weapons, with all the necessary caveats and assumptions and extrapolations about them overcoming technical hurdles," said one U.S. official. "Admittedly, those are significant assumptions."
Publicly, the Bush administration estimates that 2011 is the soonest that Iran could produce a nuclear weapon.
"They are moving much quicker than everyone thought," said the diplomat, who didn't offer an estimate on how soon Iran might be able to produce highly enriched uranium.
He said there was evidence that Iran has moved large containers of uranium hexafluoride gas to Natanz, the main enrichment research site in central Iran, from a facility in Isfahan in preparation for starting the test network.
"I think it's fair to say that there's growing concern about what the Iranians may be up to," said a U.S. defense official.
David Albright, a former IAEA inspector who closely follows the issue, said he was skeptical that Iran could produce 25 kilograms (55 pounds) of highly enriched uranium—the quantity required for a warhead—by sometime in 2008.
Albright, the director of the independent Institute for Science and International Security, said his "worst-case scenario" was 2009, due to Iran's lack of experience in operating large numbers of centrifuges, the complexities involved and the potential for numerous problems.
Iran insists that its enrichment program is intended to make fuel for power plants, not for nuclear weapons, but it admits concealing the project for 18 years from IAEA inspectors.
Moreover, Tehran has failed to reveal to the IAEA all aspects of its program, including purchases of weapons-related nuclear know-how from a Pakistani-led smuggling ring that supplied the North Korean and Libyan weapons programs. Ayhan Evrensel, an IAEA spokesman, declined to comment for this article.
A diplomat close to the IAEA confirmed that by the end of last week, Iranian engineers had assembled all 164 centrifuges of the test cascade at Natanz as they'd planned to do. They still had to finish connecting all of the machines and then would need time to conduct tests of the piping and seals, this diplomat said by telephone from Vienna, Austria.
However, the diplomat, who asked to remain anonymous because of the sensitivity of the issue, said the development conformed to the agency's timeline and that IAEA experts didn't view it with alarm.
Britain and France, backed by the United States, have proposed a statement in the Security Council demanding that Iran suspend all uranium enrichment work and setting a 30-day deadline for an IAEA report on Tehran's compliance.
Russia and China, which have major financial stakes in oil-rich Iran, opposed the proposal, contending that it paved the way for the Security Council to impose sanctions on Iran.
The crisis erupted in January when Iran ended a more than two-year suspension of enrichment work in defiance of international objections. The IAEA board of governors voted in February to refer the matter to the Security Council after the agency found that it couldn't confirm the peaceful nature of the program.
According to information Tehran provided to the IAEA, Iranian engineers first fed uranium hexafluoride gas into single centrifuges, followed by cascades of 10 and 20 machines.
It has informed the IAEA that it plans to begin installing the first 3,000 centrifuges of a 50,000-machine industrial-scale plant in underground halls at Natanz in the last quarter of this year.
One U.S. official said that if Iranian engineers successfully operate the 164-machine cascade as quickly as they did the smaller assemblies, they could move up the installation of the first centrifuges of the underground plant to within the next "few months."
If all went smoothly, he continued, those machines could begin operating in 2007 and produce enough highly enriched uranium for one nuclear warhead within about one year.
"The anxiety level has risen significantly," he said. "Iran is closer that we thought they were to mastering the operation of a centrifuge cascade."
(c) 2006, Knight Ridder/Tribune Information Services.
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