Ian Traynor in Zagreb and Kasra Naji in Tehran
The European powers secured a pledge from Iran at the weekend that Tehran would halt its uranium enrichment programme within weeks, an agreement that may avert a showdown later this month between Iran and the west.
But the agreement, reached after a marathon round of negotiations in Paris between Iran and the EU troika of Britain, France, and Germany, looks unlikely to satisfy Washington and may yet fall apart.
In the third round of talks in a fortnight, it was agreed that Tehran would suspend its entire enrichment programme until a final "grand bargain" is struck between Iran and the EU, with the EU guaranteeing nuclear, political, and trade concessions to Iran in return for it abandoning its domestic uranium enrichment, the process which could deliver fissile material for warheads.
The Paris agreement represented a partial victory for the EU. Tehran has balked at insistence on "indefinite" suspension of uranium enrichment, while the Europeans demanded the indefinite freeze until "an acceptable long-term agreement" was reached.
The weekend deal, though, remains a halfway measure for the Europeans and the Americans. The three-page proposal from the EU demands that Iran should "cease to develop or operate facilities which would give it the capacity to produce fissile material, including any enrichment or reprocessing capability".
That would strip Iran of any nuclear bomb-building capacity. It is unlikely that it will agree. But European diplomats say Iran is being offered a good deal.
Tehran, by contrast, insists on its right under international treaties to develop its nuclear industry for civil purposes.
The issue is touted as one of the biggest problems for George Bush's second term.
If the Iranians have not stopped their enrichment activities by November 25, when the board of the International Atomic Energy Agency meets in Vienna, the EU troika are likely to back Washington in taking the crisis to the UN security council in New York, which could entail sanctions on Iran.
The weekend agreement may have done enough to prevent resorting to the security council. But the brinkmanship looks likely to continue. Observers in Vienna expect a strengthened Bush administration to get tougher on Iran and be less happy with European efforts to find a settlement.
Hussein Mousavian, the chief Iranian negotiator in Paris, told Iranian television yesterday that the terms agreed still had to be endorsed by the national leadership.
"If the agreement is not approved, then the talks will have failed. But I am not pessimistic," Mr Mousavian said.
The parliament in Tehran, having rushed through a bill compelling the country to press on with uranium enrichment last week, is expected this week to add a conciliatory note with a bill renouncing nuclear weapons.
Just as the talks reached a critical stage in Paris, in Tehran the visiting Chinese foreign minister, Li Zhaoxing, told Iranian leaders his country would oppose a move to refer Iran to the security council.
Mr Li talked to the British foreign secretary, Jack Straw, and the US secretary of state, Colin Powell before flying to Tehran where he told a press conference that Iran had cooperated well with the IAEA and that referring it to the UN would only complicate matters.