President Obama recently invited me to the Oval Office for a discussion about Iran. The President reiterated to me in private what he had previously said in public: namely, that he would not allow Iran to develop nuclear weapons; that containment of a nuclear Iran was not an option; that sanctions and diplomatic pressures would be applied and increased first; but that, as a last recourse, the military option would not be taken off the table.

What the President said is now the official American policy with regard to the threat of a nuclear Iran. It is clear that sanctions and diplomacy alone will not convince the Iranian mullahs to halt their progress toward their goal of an Iran with nuclear weapons. The only realistic possibility of persuading the Iranians to give up their nuclear ambitions is for them to believe that there is a credible threat of an American military attack on their nuclear facilities. Unless this threat is credible, the Iranians will persist. And if the Iranians persist, and the Israelis do not believe that the American threat is credible, the Israelis will undertake a military strike against Iranian nuclear facilities. It is crucial, therefore, for America's military threat to be credible and to be perceived as credible by both the Israelis and the Iranians.