Israeli politicians are warning the West that Iran must not obtain nuclear weapons. Their fear is pretty rational, considering that many Iranian mullahs have openly called for nuclear strikes against Israel. From 2001:
One of Iran’s most influential ruling cleric called Friday on the Muslim states to use nuclear weapon against Israel, assuring them that while such an attack would annihilate Israel, it would cost them "damages only".
"If a day comes when the world of Islam is duly equipped with the arms Israel has in possession, the strategy of colonialism would face a stalemate because application of an atomic bomb would not leave any thing in Israel but the same thing would just produce damages in the Muslim world", Ayatollah Ali Akbar Hashemi-Rafsanjani told the crowd at the traditional Friday prayers in Tehran.
He's wrong though, of course, because the first time Muslims use nuclear weapons will also be the last.
Further, the US might be playing good-cop/bad-cop with Iran, casting Israel as the bad cop. The Muslims hate Israel more than the US already, so if someone has to take action it may as well be them. Afterwards the US can step in, protect Israel, and try to cool the situation down. This sort of strategy gets more difficult as the Islamic world starts to hate America more and more.