WASHINGTON — U.S. intelligence agencies have concluded that Iran halted its nuclear weapons program in 2003 and that international pressure has compelled the Islamic Republic to back away from its pursuit of the bomb.
The new findings represent a retreat from a fundamental U.S. assumption about one of its main adversaries, and an admission that a central component of previous intelligence estimates on Tehran's nuclear program was wrong. But the report makes it clear that Iran could decide at any point to resume its efforts to develop a nuclear weapon.
The assessment, which represents the consensus of the 16 U.S. intelligence agencies, including the CIA and the National Security Agency, is expected to have major implications for the ongoing debate over whether to confront Iran militarily or through diplomatic means, an issue that has been a source of friction within the Bush administration and with some members of the international community.
As recently as October, President Bush was warning that a nuclear-armed Iran could lead to World War III, and Vice President Dick Cheney threatened Tehran with "serious consequences" if it did not abandon its nuclear program.
Senior U.S. intelligence officials said that Bush and Cheney were briefed on the intelligence estimate on Iran Wednesday, but declined to say when they were informed that Iran had halted its nuclear weapons work.
Iran stopped developing nuclear weapons designs and ended covert efforts to produce highly enriched uranium suitable for use in a bomb, the report says.
"We judge with high confidence that in fall 2003, Tehran halted its nuclear weapons program," the report concludes.
And it says the intelligence community judged "with moderate confidence" that Tehran had not restarted the program as of mid-2007 and did not have a nuclear weapon.
At the same time, the findings, which will be shared with Israel and other U.S. allies, note that "Tehran at a minimum is keeping open the option to develop nuclear weapons."
The report says that despite threats of international economic sanctions, Iran resumed installing centrifuges at Natanz in 2006, but "still faces significant technical problems operating them."
The Natanz installation is part of Iran's much-publicized program to enrich uranium for nuclear reactors capable of generating electrical power, but the degree of enrichment necessary for so-called weapons-grade uranium is far higher than that of the fuel it is able to produce there.
The report also says that Iran is unlikely to be able to make enough highly enriched uranium for a bomb before 2009 at the earliest, and possibly as late as 2015. The acquisition of weapons-grade material is considered the main obstacle to Iran building a bomb.
The intelligence estimate was contained in a report titled "Iran: Nuclear Intentions and Capabilities."
The key judgments of that report were declassified and released Monday. The bulk of the report, which is said to span nearly 140 pages, remains classified.
The report acknowledges that emerging evidence has forced analysts to alter their views on Iran's intentions and capabilities, as well as its susceptibility to outside pressure.
"Tehran's decisions are guided by a cost-benefit approach rather than a rush to a weapon irrespective of the political, economic and military cost," according to the report. Overall, it says, Iran "is less determined to develop nuclear weapons than we have been judging since 2005," and "may be more vulnerable to influence on the issue than we judged previously."
As a result, the report could give new leverage to Secretary of State Condoleezza Rice, Defense Secretary Robert M. Gates and others within the administration who have pushed for diplomatic initiatives over military strikes against the Islamic regime.
Indeed, the document suggests, "some combination of threats of intensified international scrutiny and pressures," along with opportunities for Iran to achieve its regional goals, could "prompt Tehran to extend the current halt to its nuclear weapons program."
At the White House, national security advisor Stephen Hadley described the report as "good news" that validated the administration's approach to keeping Iran from developing a nuclear weapon.
"It tells us that we have made some progress in trying to ensure that that does not happen," Hadley said. "But it also tells us that the risk of Iran acquiring a nuclear weapon remains a very serious problem."
From Vienna, a senior official at the International Atomic Energy Agency said the report "basically validates what the IAEA has been reporting: There is no indication of a secret program, though we can't rule it out."
The report comes five years after a hastily assembled National Intelligence Estimate on Iraq erroneously concluded that the country had chemical and biological weapons stockpiled and was aggressively pursuing nuclear weapons.