At the same time, the National Intelligence Estimate (NIE) by all 16 US spy agencies cautioned that the Islamic republic was keeping its options open and could be able to make a nuclear weapon sometime between 2010 and 2015.

The NIE, which represents the consensus among all 16 US spy agencies, said the program was still dormant, and Iran's intentions unclear, but that the halt suggested Tehran was more susceptible to global pressure than had been thought.

The declassified "key findings" provided ammunition to both side in the international dispute over the best approach to Iran, and were were expected to fuel rather than quench the often bitter US debate over Iran policy ahead of the November 2008 presidential elections.

Senate Democratic Majority leader Harry Reid called on Bush to emulate former Republican president Ronald Reagan's dialogue with the Soviet Union, pushing for "a surge of diplomacy" with Tehran.

At the White House, US National Security Adviser Stephen Hadley said the NIE buttressed US President George W. Bush's strategy of piling pressure on Iran and called for increasing Tehran's economic and diplomatic isolation.

Months after Bush warned of "World War III" or a "nuclear holocaust" if the Islamic republic gets nuclear weapons, the NIE cited "high confidence" that Tehran had halted its nuclear weapons program in late 2003 and "moderate confidence" that it had not restarted as of mid-2007.

At the same time, the Islamic republic is "keeping open the option to develop nuclear weapons," according to declassified key findings of the report, which was based on intelligence available as of October 31.

"But we do not know whether it currently intends to develop nuclear weapons," according to the estimate, which came roughly five years after an NIE that overstated Iraq's weapons abilities and intentions.

"Tehran's decision to halt its nuclear weapons program suggests it is less determined to develop nuclear weapons than we have been judging since 2005," it said, adding Iran appeared to have bowed to international pressure.

"Our assessment that the program probably was halted primarily in response to international pressure suggests Iran may be more vulnerable to influence on the issue than we judged previously," it said.

The report found that "the earliest possible date" Iran could have enough highly enriched uranium for a weapon was late 2009, "but that this is very unlikely."

The NIE judged with "moderate confidence" that Iran would be able to produce enough highly enriched uranium for a weapon "sometime during the 2010-2015 timeframe," with the US State Department saying not before 2013.

The office of the US Director of National Intelligence described the document as "an extensive reexamination" of its previous May 2005 assessment of Iran's nuclear ambitions.

"The bottom line is this: for that strategy to succeed, the international community has to turn up the pressure on Iran -- with diplomatic isolation, United Nations sanctions, and with other financial pressure -- and Iran has to decide it wants to negotiate a solution," said Hadley.

Iran denies Western charges that it seeks nuclear weapons under cover of a civilian atomic energy program, and has drawn UN sanctions for refusing to freeze its uranium enrichment, which can yield materials for a nuclear bomb.

Washington recently slapped unilateral sanctions on Iran, and has been pushing for a third round from the United Nations.

In 2003, Iran's president was the reform-minded Mohammad Khatami, who was replaced by Mahmoud Ahmadinejad, whose hardline approach and fiery anti-Israel rhetoric has sharply increased tensions with the United States.

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