Paris "expressed its disappointment at the lack of a clear response from Iran" to the proposals, the ministry said in a statement.

The warning came after a telephone conversation with the European Union foreign policy chief Javier Solana, who held what a spokesman described as "inconclusive" talks with Iran's top nuclear negotiator, Saeed Jalili, after Tehran missed a deadline to respond to the compromise offer.

A US State Department spokesman said senior diplomats from the United States, Britain, France, Germany, Russia and China discussed developments and agreed to push for new action if Iran continues holding out.

"France understands that a written document must reach Mr Solana tomorrow, August 5, and hopes that this document will contain the answer that the international community is waiting for," the French foreign ministry said.

"In the absence of a positive response to the six (world powers), Iran will then have to face new sanctions," it said.

Earlier, France's deputy ambassador to the United Nations, Jean-Pierre Lacroix, said: "If we don't get an encouraging response from the Iranians, we will have to show firmness, resort to sanctions as in the past."

His comments were echoed by the British Foreign Office.

"We will have no choice but to ask the UN to proceed with further sanctions," a foreign office spokesman said Monday.

The United Nations has imposed three sets of sanctions against Iran over the nuclear dispute and is mulling a fourth round of measures.

Tehran has steadfastly refused to suspend its uranium enrichment activities, which it says are aimed only at producing fuel for nuclear power production.

The United States and its allies fear the program is a cover for developing nuclear weapons.

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