His outspoken remarks, which drew a parallel between Iran and Iraq, appeared to take aim at the US and Britain. They followed comments on Sunday night by the French foreign minister, Bernard Kouchner, who said: "We have to prepare for the worst," adding "the worst is war".

"I would not talk about any use of force," Mohamed ElBaradei told reporters at the International Atomic Energy Agency headquarters in Vienna. "There are rules on how to use force, and I would hope that everybody would have gotten the lesson after the Iraq situation, where 700,000 innocent civilians have lost their lives on the suspicion that a country has nuclear weapons."

There has been a string of reports out of Washington that the Bush administration is running out of patience with diplomacy and is intensifying its plans for air strikes as a means of halting Iran's disputed nuclear programme.

UN officials said Mr ElBaradei, an Egyptian diplomat who was awarded the Nobel peace prize in 2005, was attempting to slow down what seemed to be an accelerating march to war.

"There's a strategic reason for doing these things," one official said. "He really is alarmed. He sees this thing going out of control. The feeling around here is that this looks like the run-up to the Iraq war."

Last month, the French president, Nicolas Sarkozy, sparked a heated political debate in Paris when he called the Iranian stand-off "the greatest crisis" of current times, saying the world had "a catastrophic alternative: an Iranian bomb or the bombing of Iran".

Following Mr Kouchner's comments, Tehran yesterday denounced France's stance on the nuclear issue, which has toughened since Mr Sarkozy's election in May. Iran's state-owned news agency IRNA published an editorial accusing Paris of "extremism" and pandering to Washington. "The new occupants of the Elysée want to copy the White House," it said, accusing Mr Sarkozy of taking on "an American skin".

Iran insists on its right to run a comprehensive nuclear programme, including the enrichment of uranium, which it says is intended for peaceful electricity generation.

The US has called a meeting of senior European and Russian officials in Washington on Friday to discuss the deepening crisis over Iran. Britain, the US and France are likely to push for more sanctions over Iranian defiance, while Russia and China are expected to resist, pointing to a deal Mr ElBaradei struck with the Iranian government last month, in which Tehran agreed to answer unresolved questions over its nuclear programme.

The US, Britain, France and Germany complained to Mr ElBaradei that they had not been consulted and that the agreement did not mention the UN Security Council's demand that Iran suspend uranium enrichment while its programme is assessed. In their eyes, the deal gave Tehran a means of stalling new sanctions while continuing to produce nuclear fuel.

France is determined that if the UN is unable to agree on a new round of sanctions against Iran, the European Union should impose its own. Mr Kouchner said leading French companies such as Total and Renault had been urged not to sign new contracts with Iran, and he flew to Moscow to try to persuade Russia to accept a toughening of the embargo.

Meanwhile, the French prime minister, François Fillon, yesterday tried to play down the talk of war, saying that everything must be done to avoid a conflict, but he added that Mr Kouchner was right to stress the danger and seriousness of the Iranian stand-off.

A British official said yesterday that when the French foreign minister had raised the spectre of a conflict, he was "stating the obvious".

"The worst case scenario is a war with Iran, but meanwhile we are seeking a diplomatic solution," the official said.

The French Socialist leader François Hollande yesterday called for an immediate parliamentary debate on Iran, demanding to know if the government had new intelligence on Iran's nuclear intentions.

After talks with Mr Kouchner in Paris yesterday, the Dutch foreign minister Maxime Verhagen said the Netherlands would support EU sanctions if the UN Security Council failed to agree new measures.

Mr ElBaradei, the director general of the IAEA, has been increasingly at odds with Washington and London, who believe he is straying beyond his job description and freelancing as an independent statesman.