"In parallel to negotiations on a new [UN] Security Council resolution, which must be pursued, I propose that we start right away exploring together the possibility of new European measures", the letter cited by media reports says.

"Time is working against us, since each day Iran moves closer to mastering the technology of enrichment, which means a de facto military nuclear capacity", it continues.

Mr Kouchner's letter is yet another sign of Paris adopting a tougher line on Iran compared to the approach followed by former French president Jacques Chirac.

Speaking in the United Nations last week, French president Nicolas Sarkozy also suggested "a new layer of economic sanctions at EU level".

Earlier, Mr Kouchner indicated "we have to prepare for the worst [with Iran] and the worst is war" – a comment that he later apologized for.

According to AFP, only the UK has "wholeheartedly" backed Mr Kouchner's call for an independent EU line. Other governments - especially in Berlin, Rome, Madrid and Vienna - are not in the mood to follow that path and prefer instead to keep the debate under the UN Security Council umbrella.

The New York-based body is currently waiting for two key reports on Iran's cooperation with the international community - one drafted by the UN's nuclear watchdog and another one by the EU's chief diplomat Javier Solana.

"Italy has never ruled out possible European sanctions, but we should also remember that we would have a bigger price to pay than those who shout the loudest", foreign minister Massimo D'Alema told ANSA news agency.

"We should...not take a second step before we've taken the first", Austrian foreign minister Ursula Plassnik said at the United Nations last week, AFP reports. "International pressure is most effective when it's based on broad international support. Only the UN Security Council can provide that support", she added.

France's Mr Kouchner will have a chance to persuade his counterparts during their regular meeting - scheduled for 15 October.

"That will set off a debate. We'll see what the reaction of the other ministers will be", the spokesperson for the Portuguese EU presidency Manuel Carvalho told AFP.

In the past, the European Union has offered major economic and political incentives if Iran would suspend its controversial activities - something that Teheran refuses as an unacceptable precondition.