"This is the policy we want to continue with, while understanding the need to be firm. We cannot accept another atomic bomb in the region," said Kouchner, whose country holds the EU's rotating presidency.
But, four days ahead of fresh talks in Geneva between EU foreign policy chief Javier Solana and Iran's nuclear negotiator Saeed Jalili, Kouchner held out little hope of a breakthrough.
"I have talked for a long time with the Iranians, many hours," he said. "There was nothing fundamental that was advancing. We will continue but I have to say we have already tried very hard."
World powers — Britain, China, France, Germany, Russia and the United States — last month presented Iran with an offer aimed at ending the five-year-old nuclear crisis, notably offering Tehran technological incentives in exchange for suspending the sensitive process of uranium enrichment.
Iran has proposed its own package — a more all-embracing attempt to solve the major security problems of the world — and has made much of the common ground between the two proposals.
France has, however, confirmed that Iran does not say in its response that it is prepared to suspend uranium enrichment, which world powers fear Tehran could use to make a nuclear weapon.
"For the moment, the answer has always been: 'we really want to talk but not about enrichment'," Kouchner said.
But diplomats say the major powers have offered to start "pre-negotiations" over a six-week period during which Tehran would add no more uranium-enriching centrifuges and in return no further sanctions would be imposed.
