let's assume the worst: say Iran is working on a bomb; say it acquires one in the next few years. Only Benjamin Netanyahu and assorted American neoconservatives believe - or pretend to believe - that Iran might actually use it, given Israel's overpowering ability to strike back.
McLaughlin & Associates poll from May 2009:
If Iran is able to produce a nuclear weapon, nearly eight in ten voters (79%) say it is likely that Iran will provide nuclear weapons to terrorists to attack an American city.
American Neocons: 240 million strong--and growing.