In an interview with the Israeli newspaper Haaretz Thursday, Mitt Romney declared a nuclear-armed Iran to be the gravest foreign policy threat:
I have said in the past and I can reiterate now that it is essential that Iran does not become nuclear. A nuclear Iran represents the greatest threat to the world, to the United States and to the very existence of Israel. A nuclear Iran would mean that Hezbollah or other actors would potentially someday be able to secure fissile materials which would threaten the world.
Romney refrained several times from directly criticizing President Obama over Israeli policy and noted that both he and the president have "said that a nuclear Iran is unacceptable." Iran is never far from Romney's lips when talking about foreign policy, but in the past he's referred to Russia as America's "No. 1 geopolitical foe."
Romney criticized Russia in the Haaretz interview for standing in the way of U.N. resolutions that would aid the rebellion in Syria.