Sy Hersh says just that in the New Yorker.
The article is lengthy but worth a read. The nuclear weapons in question are bunker-busters that would be used in an attempt to take out underground Iranian command and control. The neocons are hot to use tactical nukes. Many senior officers and officials have said they will resign if the US uses offensive nukes and there is good reason to believe for this reason alone, no nukes will be used.
Some highlights. Everyone, including the IAEA, believes Iran is working on nuclear weapons but there is no clear proof, and everyone agrees that it would be a bad thing for Iran to get a bomb and the ability to deliver a nuclear weapon.
There is disagreement on how many years away Iran is from such a bomb. There seems to be a general consensus of 5 to 10 year. The Bushies think it's immanent and their credibility is so shot that on one believes them.
Further the Bushies have learned nothing from Iraq and again want regime change in Iran as a goal. The rest of the world just wants no nukes.
The Bushies apparently believe that by relentlessly bombing and humiliating the Iranians that they will throw out their government and abandon radical Islam. The rest of the world marvels at the unrelenting ignorance of the Bushies. The rest of the world, including the non-neocon conservatives, worries that the consequences of even a massive conventional strike (the Bushies only do massive) hitting hundreds of target will have catastrophic consequences, and cementing support for a government that is now on the verge of collapse.
Some House members worry that Bush has a messianic complex and that he sees Iran as his legacy. They think this is bad.