Iran unlikely to commit collective suicide by threatening U.S. with nuclear weapons
So although a renewed Shiite messianism does create some cause for concern about the potential uses of an Iranian bomb — in particular because it suggests that Ahmadinejad may be more a utopian than a realist — it is almost certainly a mistake to anticipate that Iran would use its nuclear power in a way that would provoke large-scale retaliation and assured self-destruction. Iranian leaders have been more than ready to sacrifice their own citizens in large numbers. During the Iran-Iraq war, major efforts went into recruiting young boys to the Basij militias, which were then sent to the front lines on what were essentially suicide missions. Religion played the central part in motivating the teenage soldiers, and it is reasonable to believe that religion helped salve the consciences of those who ordered these children into battle. Yet even this discounting of the value of human life — in a war started by Saddam Hussein, not by Iran — fell short of voluntarily putting an entire nation at risk. Ahmadinejad surely understands the consequences of using a nuclear bomb, and Shiite Islam, even in its messianic incarnation, still falls short of inviting nuclear retaliation and engendering collective suicide.
The Iranian regime probably can be deterred, either from using its nuclear arsenal or from taking other aggressive actions in the belief that its nuclear arsenal will itself deter countermoves by the United States or other states. Although willing to tolerate very high costs when core interests are threatened, key members of this regime -- including Khamenei and Rafsanjani --have also demonstrated that they will concede in the face of heavy damage and are often unwilling to suffer more modest damage when their core interests are not threatened.
Despite Iran's fiery rhetoric, it is unlikely that the Iranian regime would risk certain destruction by pre-emptively attacking Israel.