"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 Administration perception continues, generated primarily by Iran's nuclear program but intensified by Iran's military assistance to armed groups in Iraq and Afghanistan and to Hamas and Lebanese Hezbollah. However, the threat perception of other governments might change following the December 3, 2007 release of key judgements from a new National Intelligence Estimate (NIE) that indicates that Iran is likely not on a drive to develop an actual nuclear weapon. The Bush Administration argues that the NIE at least partly validates its approaches to containing the potential threat posed by Iran -- strengthening international economic and political isolation of Iran to compel it to comply with international demands that it curb its program. Still, the NIE does not claim that Iran has complied with U.N. Security Council demands that it cease uranium enrichment. Two U.N. resolutions (1737 and 1747) ban weapons of mass destruction (WMD)- related trade with Iran, 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. With Iran still refusing to comply on enrichment but apparently mostly cooperating with an August 2007 offer to reveal to the International Atomic Energy Agency additional information on its past nuclear program, further sanctions, possibly including on civilian trade or financing, have been under discussion at the U.N. Security Council. […] Some in the Administration believe that only a change of Iran's regime would end the threat posed by Iran."
CRS Report for Congress, RL32048