The move was seen as an attempt by the government to prevent its nuclear programme from coming to a sanctions vote in the UN.

"If the issue is returned to the International Atomic Energy Agency, we will be ready to allow intrusive inspections, " Mohammed Saeedi, Iran's deputy nuclear chief said.

Mohamed ElBaradei, the IAEA chief, confirmed in a report on Friday that Iran has produced enriched uranium and defied a UN Security Council deadline to halt all activities related to uranium enrichment.

The IAEA report brought swift reactions from nations concerned with Iran's nuclear development.

US president George Bush said the world was concerned about Iran's "desire to have not only a nuclear weapon but the capacity to make a nuclear weapon". Bush added he was not discouraged by Iran's vow to defy world pressure, saying: "I think the diplomatic options are just beginning".

US ambassador John Bolton took a tough line, saying "the IAEA report shows that Iran has accelerated its efforts to acquire nuclear weapons. . . We're ready to proceed; we're ready to move expeditiously.

And what comes after that is largely in Iraq's hands. They have to comply or the Security Council is free to take other steps."

ElBaradei's report may spark a divisive debate in the Security Council when foreign ministers of its five permanent members plus Germany meet on 9 May to discuss the next step.

France and Britain have joined the US in supporting strong action against Iran, while Russia and China want the IAEA to take the lead in finding a diplomatic solution.

Russia's deputy UN ambassador Konstantin Dolgov said: "Sanctions are not the way of resolving the Iranian problem, at least at the current stage, bearing in mind the information available."

Iran warned that it "does not respond well to pressure". Iran's ambassador to the UN, Javid Zarif, said his country was seeking to resolve the crisis over its nuclear programme.

"There is a multitude of possibilities for reaching a solution, if we start from the basic assumption that Iran has the right (to nuclear power) f and Iran should not develop nuclear weapons, " he said.

Iran barred intrusive inspections of its nuclear facilities in February after it was referred to the Security Council over nuclear activities that several Western countries suspect are aimed at producing warheads. Tehran says its programme is for peaceful purposes.

Saeedi said Iran was also ready to address the concerns of the US and its allies over Iran's nuclear programme in negotiations. The Iranian nuclear negotiator said his country had told the IAEA in a letter on Thursday that it was ready to answer questions if its dossier was returned for investigation.

Top Iranian officials, including president Mahmoud Ahmadinejad, have repeatedly vowed that Iran will not halt enrichment activities.