Hmm...I think this comes down to whether you believe a) that Don Rumsfeld's funky bunky busters will work without destroying all Baghdad and 12 million Civpop (which I don't for a minute) and b) that Iraqi military targets exist which are both worth a nuclear strike and more importantly c) cannot be destroyed/neutralised by conventional or political means with less needless destruction and political blowback. We can't assume that a "bunker buster" will be any less horrific than an ordinary tacnuke - so the assumption has to be that any strike will be as bad as one fears. Therefore I don't think that a pre-emptive use of a nuclear weapon in Iraq could be justified, as we can expect to dominate the conventional battle. As in the original war, the only purpose for them would be deterrence of the use of WMD by the other side.