A warning by France's foreign minister that the world should prepare for war over Iran's nuclear programme has drawn an angry response from Iran.
Bernard Kouchner said a nuclear-armed Iran would be a grave threat
Iran's foreign ministry said the remark had damaged the credibility of France, while the official Iranian news agency accused Paris of aping Washington.
On Sunday France's Bernard Kouchner said: "We have to prepare for the worst, and the worst is war."
Meanwhile, the top UN nuclear official said force should be a last resort.
At a conference of the UN nuclear watchdog, the International Atomic Energy Agency (IAEA), in Austria, Mohamed ElBaradei said he saw no clear and present danger, and that talk of force was counter-productive.
Iran denies it is trying to acquire nuclear weapons, and says it only wants nuclear power to generate electricity for civilian purposes.
But it has repeatedly rejected UN demands to give up the enrichment of uranium, which the US and other Western states fear is being diverted to a nuclear weapons project.
Mr Kouchner said negotiations with Iran should continue, but that an Iranian nuclear weapon would pose "a real danger for the whole world".
He said a number of large French companies had been asked not to tender for business in Iran.
Iran says its nuclear programme is peaceful
Iranian official media responded with contempt.
"The occupants of the Elysee (the French presidential palace) have become the executors of the will of the White House and have adopted a tone that is... even more inflammatory and more illogical than that of Washington," IRNA news agency said.
On Monday Mr Kouchner said even in the absence of UN action, the European Union should prepare its own sanctions against Iran.
Following talks in Paris, his Dutch counterpart Maxime Verhagen said his government would be willing "to apply EU sanctions in common with the United States sanctions".
Mr Kouchner later travelled to Moscow, where he is to hold talks with his counterpart Sergei Lavrov on Tuesday.
Russia has a UN Security Council veto over any new sanctions, and its support is seen as vital for any new approach to try to force Iran to give up enrichment.
Iran has warned that any new punishments could push it to stop co-operating with the IAEA.
The US and its allies believe a IAEA agreement with Iran to clear up questions about its past nuclear activities just gives Iran more time - delaying new UN sanctions while advancing its nuclear capabilities.
The BBC's diplomatic correspondent Jonathan Marcus says France has changed its approach to world affairs under its new President Nicolas Sarkozy, adopting a harder line on several issues, and seeking to improve relations with the US.
The United States has not ruled out a military attack against Iran to prevent it from acquiring a nuclear weapon.
However, a top general in Iran's elite Revolutionary Guards said any bombing raid on targets in Iran would provoke a tough response.
US positions in neighbouring Iraq and Afghanistan "are within our range", Gen Mohammad Hassan Koussechi told IRNA.