A Foreign Office official said Britain would discuss "next steps" with its international partners at an emergency meeting of the International Atomic Energy Agency on Tuesday.

"We're not going to speculate on the outcome of that meeting," the official told AFP in London.

"However, our position is well known. Were Iran to resume any part of its uranium enrichment-related activities, including the uranium conversion facility at Isfahan, this would be a breach of the Paris agreement which they signed on November 15, 2004 as well as IAEA board of governors resolutions."

Britain, which currently holds the rotating European Union presidency, has been working with fellow EU heavyweights France and Germany to diplomatically stop Iran from developing nuclear weapons.

Mohammad Saidi, vice president of Iran's Atomic Energy Agency, said earlier Monday in Isfahan that Iran has "resumed the conversion of uranium under the supervision of the IAEA".

The move, which risks seeing Iran hauled before the UN Security Council, comes after Iran rejected as "unacceptable" a package of EU proposals aimed at guaranteeing that it was not trying to build a nuclear weapon.

Tuesday's emergency IAEA meeting in Vienna, requested by the European Union, is expected to put forward an ultimatum demanding a commitment from Tehran to suspend nuclear fuel work.

The crisis has escalated since Iran's ultra-conservative President Mahmood Ahmadinejad took office last week, with the new leader on Monday putting a fellow hardliner in charge of the nuclear dossier.

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