If we assume that Israel's gov't consults with the White House prior to launching a nuclear retalliation, the White House would probably say "no" anyway. Do you seriously think that General Sharon would care what we think? I doubt it. So, the real problem is that US agents, operatives, and advance teams will be in Baghdad and other areas or Iraq snooping for WMD and scooping targets. Then, suddenly a nuke from Israel wipes out communication with field operatives, fries all international satillite links, and then toasts our planning.
With friends like that, no wonder they're spying on the nation who set them up!
Regarding biological weapons, Israel has some good medical facilities but I doubt that they will be able to identify anthrax within 72 hours of when the strike occurs. It is more likely that anthrax will be laced into other things. If IDF or emergency crews respond and are unknowingly exposed, they will present symptoms several days later. By that point, the war could be over.