"According to the Administration's 'National Security Strategy' document released on March 16, 2006, the United States 'may face no greater challenge from a single country than Iran.' That perception, generated primarily by Iran's developing nuclear program, has been intensified by Iran's assistance to Shiite armed groups in Iraq and to Lebanese Hezbollah. U.S. officials also accuse Iran of refusing to bring to justice several senior Al Qaeda activists in Iran. U.S. officials further cite Iran for causing the deaths of U.S. troops by providing arms and other material assistance to Shiite Islamist militias participating in escalating sectarian violence against Iraq's Sunnis. In part to direct regional attention to that view but also to engage Iran on an Iraq solution, the Administration supported and attended regional conferences on Iraq on March 10, 2007, and May 3-4, 2007, both attended by Iran (and Syria). The Bush Administration is pursuing several avenues to attempt to contain the potential threat posed by Iran, but the U.S. focus is now on multilateral - and to some extent bilateral - diplomacy. Iran has not complied with repeated U.N. Security Council deadlines since August 2006 to cease uranium enrichment, resulting in two U.N. resolutions (1737 and 1747) to date that ban trade with and freeze the assets of Iran's nuclear and related entities and personalities, prevent Iran from transferring arms outside Iran, and require reporting on international travel by named Iranians."
CRS Report for Congress, RL32048