IBTZ2!!! You assume that Iran won't have a bomb for 5 years. We need to assume that they will have it this year, because that is possible.
They tested their first A-Bomb on 29 August, 1949.
Consider also that the Soviet program was accelerated by their spies, but Iran doesn't need to spy on us or anybody else if Kim Jong Il is willing to share his tech, or if Putin lets one of his scientists get loose. There were almost certainly people in Iraq who knew how to build a bomb, and we know a junior at Princeton figured it out back in the 70's, so it's not the hardest thing in the world to do.