In one of the strongest warnings yet over Iran's disputed nuclear program, German Foreign Minister Joschka Fischer said such a move would "collapse" the talks but stressed that negotiations with Iran were for now continuing.

"It is the foundation of the talks that the uranium enrichment remains suspended," Fischer told reporters on the sidelines of an international conference to review the 1970 nuclear non-proliferation treaty (NPT).

If the Islamic regime restarts enrichment, he said, "this would lead to a collapse of the talks."

Iran has insisted that its nuclear program is intended for peaceful, civilian energy purposes and stopped enriching uranium as a confidence-building measure for negotiations with the European Union that were launched in December.

But Tehran, which US President George W. Bush lumped into his famed "axis of evil" and which Washington says could be chasing the atomic bomb, is awaiting a response on a proposal it has made to resume limited production of enriched uranium, which makes fuel for nuclear power reactors, but which can also be the explosive core of atom bombs.

Tehran unhappy

Iranian representatives said after talks with EU negotiators Britain, France and Germany in London on Friday that they were tiring of waiting for a European yes or no.

Tehran is unhappy with the progress of the talks and may resume uranium conversion activities in defiance of an agreed suspension of such nuclear fuel cycle work, top negotiator Hassan Rowhani said in Tehran over the weekend.

"The current process cannot continue in the way the Europeans want it to, and Iran could take new decisions," said Rowhani, the secretary of Iran's Supreme National Security Council.

On Friday, Iranian negotiator Cyrus Nasseri, quoted by the regime's official news agency, said Tehran "will perhaps be forced" to resume part of its enrichment "in the absence of an agreement" with the European Union.

The European trio is insisting however that Iran must give up all nuclear fuel activity to provide "objective guarantees" it will not seek to make atomic weapons.

The issue is one of several key questions, along with North Korea's nuclear program, that will be hotly debated during the month-long NPT conference taking place at the United Nations in New York.

Nuclear goals?

The United States, which backs the EU diplomatic initiative but is not party to the talks, charges that Iran is secretly developing nuclear weapons and must be prevented from obtaining the weapons capability which enrichment represents.

Washington has threatened to drag Iran before the UN Security Council for possible international sanctions if it resumes any enrichment activities.

But on Monday, US Secretary of State Condoleezza Rice
expressed renewed support Monday for European efforts to talk Iran out of its suspected nuclear arms program despite fears the negotiations could collapse.

Rice (photo) made her remarks after talks here with French Foreign Minister Michel Barnier, whose country is working along with Germany and Britain to wean Tehran off its suspected nuclear ambitions with economic and security incentives.

"I reiterated to the foreign minister our support for the EU-3 negotiations with Iran that are aimed at getting Iran to give confidence to the international community," Rice said.

Mohamed ElBaradei, head of the International Atomic Energy Agency (IAEA), the UN's nuclear watchdog, on Monday said that Iran should refrain from unilaterally resuming any enrichment activities.

"I hope that both parties will continue to talk," he told reporters.

Iranian negotiator Nasseri told AFP ahead of Friday's London meeting: "Our point is we simply do not have much time. We have a fuel program and we can't hold it much further."