"We are not the ones who have to decide whether to accept what they want to impose on us," Kouchner told RTL radio. "No, this is not the way it is done."
Iran said at the weekend that it had until the end of January to reach agreement on a deal to swap uranium for nuclear fuel after rejecting a December 31 deadline set by world powers.
Kouchner said Iran was trying to "side-step" the issue by "giving an ultimatum to those who have offered to help them, that is the international community including France."
Turning to opposition protests challenging the Iranian regime, Kouchner said the establishment was "under threat by very determined people, some of them very religious, and by the Shiite leadership.
"There is enormous repression. We must condemn those that cause unarmed protesters to be exposed to bullets, arrests and very severe convictions including death sentences," he added.
Scores of opposition activists, protesters and journalists have been arrested since clashes during the latest major demonstration on December 27 that left at least eight killed.
