"The issue of Iran and its nuclear program has emerged as a top priority for the Obama Administration. The sense of impending crisis is generated by growing suspicions in the international community that Iran's nuclear program is not for purely peaceful purposes, and the determination of the government of Israel, in particular, that it might take unilateral military action against Iran's nuclear facilities if its progress is not soon halted. The United States also sees a threat to U.S. interests posed by Iran's support for militant groups in the Middle East and in Iraq and Afghanistan. U.S. officials accuse Iran of helping Syria's leadership try to defeat a growing popular opposition movement and of taking advantage of Shiite majority unrest against the Sunni-led, pro-U.S. government of Bahrain. Tensions have been particularly elevated since Iran's late-December 2011 threat to try to choke off much of the world's oil supplies by attempting to close the Strait of Hormuz--a reaction to the imposition of significant sanctions against Iran's vital exports of oil."
CRS Report for Congress, RL32048