IMO
Here's the deal.
Like two gunfighters in the street, each waiting for his opponent to make the slightest move.
Then the fecal material collides with the ventilator.
We are already at war with Iran, have been since the Carter days, only difference now is it is going to get really hot, very soon.
Don't be ridiculous.
If and when there is an Islamic nuke, it will not be pointed at us; it will be pointed at Israel. Even with it's last, dying breath, the Iranian regime would still launch the nuke against Israel, even with American troops on the front porch of the Iranian President's tent (or whatever he lives in).
The real danger to us of an Iranian nuke is not that we'll receive one on the end of an ICBM, nor that we'll have it delivered to us in New York or Boston via briefcase; the real danger is the ability to threaten our allies and the Straits of Hormuz.
Now, make all the wild-Tom-Clancy-like prognostications about Ahmedinijad (whatever) and his kooky ideas about 12th imams and such, the weapon(s) would still have to be launched by military men, the vast majority of whom are certainly often more pragmatic, rational and realistic than their political masters. You're making the assumption that all the Iranian generals and their sub-commanders (who would have physical control of the weapons)are all also 12th imam-Allah-told-me-Jell-O-is-the-food-of-the-Antichrist types, who do not care about or recognize, the consequences of their actions.