Hrm... I didn't read the original in french, but according to this analysis, Chirac's latest nuke bluster was aimed as much at the US as at Iran... and perhaps more so.
Not that there's any danger that the French are going to support war, let alone nukewar, with the US... the article is careful to point out just how relentlessly discredited Chirac is at home. But in terms of understanding the various complex triangulations around Iran, this makes the Bush administration's reticence all the more understandable.
(Now, I personally think that Ahmadinejad is trying to sucker us into attacking, at which point it will be proven that there was nothing but civilian nukepower apparatus -- this would do us more foreign-policy damage than anything else he could possibly do, and it would all be self-inflicted. So as I read the game, Chirac's batting for geopolitical stability here doesn't bother me in the least.)