Not according to many current and former Israeli and U.S. officials. Following are just a few recent quotes opposing that notion from a thorough and useful compilation by the folks at Just Foreign Policy:
Iran poses a serious threat, but not an existential one.
– Dan Halutz, Former Israeli Defense Force Chief of Staff, YNet, February 2, 2012
I think the Iranian leadership is composed of very rational people.
– Lt. Gen. Benny Gantz, Israeli Chief of Staff, Haaretz, April 25, 2012
Any war with Iran would be a messy and extraordinarily violent affair, with significant casualties and consequences.
– Colin H. Kahl, former US Deputy Assistant Secretary of Defense for the Middle East, Foreign Affairs, March/April 2012