Iranian Defiance Of U.N. Detailed

Zalmay Khalilzad, U.S. ambassador to the United Nations, urges action. (Mary Altaffer - AP)

Iran has said that it is interested only in peaceful uses of nuclear energy, allowed under the Non-Proliferation Treaty, and has denied that it is working toward a nuclear weapon.

The nuclear part of the administration's long-term Iran strategy, designed by the State Department and European allies, offers Iran significant economic and diplomatic cooperation and a steady supply of enriched uranium produced outside the country for energy use in exchange for suspension. So far, Iran's refusal to accept the offer has led to the two unanimous Security Council resolutions -- weakly worded, in the view of administration hard-liners.

Bush last year also authorized diplomatic, intelligence, political and military measures targeting Iranian interests in the Middle East. Some of the measures, which followed decades of disruptive, classified activities authorized by previous administrations since relations with Tehran were severed in 1979, have been carried out with other governments in the region, officials have said. They include efforts to counter Iranian backing of Hezbollah in Lebanon and recently increased Iranian support for the Taliban in Afghanistan. The authorization also led several months ago to the arrest of a handful of Iranian operatives in Iraq.

During the enrichment process, uranium is rapidly spun in centrifuges. Yesterday's IAEA report said that during a surprise visit on May 13, nuclear inspectors found eight operating enrichment cascades -- each with 164 centrifuges, for a total of 1,312 -- being fed uranium hexafloride at the underground facility near the town of Natanz. Five additional cascades were in various stages of completion. The number was more than four times the total number of centrifuges operating at the time of the last IAEA report, in February.

Although the total was far from the 3,000 centrifuges that Iranian President Mahmoud Ahmadinejad predicted would be operating by May, some nuclear experts said that point could be reached by early summer. The glass "is a little more than half full," said David Albright of the Institute for Science and International Security in Washington.

But the level of enrichment -- less than 5 percent -- is substantially lower than the 90 percent required to make a nuclear weapon, and it is unclear how much Iran is producing and how smoothly the complicated machines are operating. U.S. government and outside analysts differ on when Iran would be able to produce a bomb, with estimates ranging from 2009 to 2015. The United States and its European partners are sending their top nuclear specialists to the IAEA next week to share information, more fully understand Iran's capabilities and reach consensus on a timeline.

Staff writer Colum Lynch at the United Nations contributed to this report.