In a major diplomatic shift, the US now says it will join its European allies in direct negotiations with Iran over its nuclear programme, once Tehran suspends the uranium enrichment that many suspect is aimed at securing a nuclear weapon.
The change, which follows an intense policy debate in Washington, was announced yesterday by Condoleezza Rice, the Secretary of State. It came on the eve of talks in Vienna where foreign ministers of the five permanent members of the United Nations Security Council will try to finalise a carrot-and-stick package, combining incentives for Tehran to scrap its enrichment programme with the threat of international sanctions if it does not.
Iran's government had a choice, Ms Rice said. It could continue its course of defiance, and "incur only great costs". Alternatively, it could work towards a solution, by halting all enrichment and reprocessing activities, and fully co-operating with the International Atomic Energy Agency, the UN's nuclear watchdog agency.
As soon as Iran "fully and verifiably" suspended its enrichment and reprocessing activities, "the United States will come to the table with our EU-3 colleagues and meet with Iran's representatives". If they take place, they would be the first formal direct negotiations in an international framework since the two countries severed relations after the country's Islamic revolution in 1979.
But Washington's new gambit leaves many uncertainties - above all on what sanctions, if any, will be acceptable to Russia and China, both veto-wielding members of the Security Council. Experts said they would probably have to be very narrowly framed, in a way that did not jeopardise the two countries' substantial economic and energy ties with Iran.
Pressed on the issue, Ms Rice refused to predict that Moscow and Beijing would definitely go along. She pointedly noted that, if all else failed, Washington might sidestep the UN and press for an agreement on sanctions "by like-minded countries". Questioned further, she did not rule out military action as a last resort.
There was "a strong international consensus that Iran cannot have nuclear weapons, and must adhere to international standards". Nonetheless, the emphasis in the US yesterday was overwhelmingly on the diplomatic route.
"We want a diplomatic solution, and I believe this problem can be solved diplomatically," President Bush said in the Oval Office, after talks with Paul Kagame, the visiting President of Rwanda. He stressed the need for a united international front, and again insisted the US, for all its differences with the government in Tehran - on terrorism and Iraq as well as on the nuclear issue - had no quarrel with the Iranian people.
Ms Rice's speech represents a significant victory for pragmatists in the administration over how to handle Iran. It is a clear setback for hardliners, led by Vice-President Dick Cheney, who have advocated a policy of no concessions, backed by more or less overt threats of military action.
But, analysts said, the White House and State Department have also bowed to pressure from the Europeans and others, who have insisted the thus-far fruitless negotiations led by Britain, France and Germany would have a much greater chance of success if the US took part as well.
Direct US participation would be "the strongest and most positive signal of our common wish to reach an agreement with Iran", Javier Solana, the European Union's foreign policy chief, said yesterday, as the announcement came from Washington. Nonetheless, Ms Rice rejected any "grand bargain" with Tehran which would include the restoration of normal diplomatic relations.
The question now is how Iran will respond. "It's possible they could meet this with a concession of their own," said Joseph Cirincione, an Iran specialist at the Carnegie Endowment in Washington, noting that Iran in the past had suspended its enrichment programme for limited periods, as a condition for talks with the EU three.
Margaret Beckett, the Foreign Secretary, yesterday promised that the Europeans would offer "a serious and substantial" package. It would show Iran the benefits of compliance, "rather than the further isolation which would result from their failure to do so".
29 JANUARY 2002 President George Bush accuses Iran, Iraq and North Korea of being an "axis of evil"
3 JANUARY 2006 The US warns Iran against resuming atomic fuel research and says the international community may consider additional measures against Iran
14 FEBRUARY Iran announces it has resumed uranium enrichment after reopening its mothballed facility at Natanz
29 MARCH UN Security Council urges Iran to halt uranium enrichment. Iran refuses to comply
5 MAY Kofi Annan, the UN secretary general, urges US to join European countries in negotiations with Iran. Some influential US politicians, including the Republican Senator John McCain, urge talks
8 MAY Mr Bush receives a letter from President Ahmadinejad detailing alleged US foreign policy misdeeds and defending scientific research. Mr Bush says it does not say when Tehran will abandon its nuclear programme
31 MAY In a major policy shift, Condoleezza Rice, above, says the US is willing to join multilateral talks with Iran if Tehran suspends its nuclear enrichment programme