"According to the Administration, Iran is a major national security challenge for the United States. The Administration perception is generated primarily by Iran's nuclear program but is compounded by Iran's military assistance to armed groups in Iraq and Afghanistan and to the Palestinian group Hamas and Lebanese Hezbollah. However, the threat assessment of some other governments was lessened by the December 3, 2007 key judgements of a National Intelligence Estimate (NIE) that indicates that Iran is likely not on a drive to develop an actual nuclear weapon. […]To strengthen its diplomacy, the Administration has maintained a substantial naval presence in the Persian Gulf. The Administration has been strongly denying widespread speculation that it plans military action against Iran, but has refused to rule it out if no other efforts to curb Iran's uranium enrichment program succeed. Some in Congress seek to limit the President's authority to take unilateral military action against Iran. Some legislation passed by the House in the 110th Congress, including H.R. 1400 and H.R. 957, would increase U.S. sanctions on Iran -- both the U.S. trade ban and the Iran Sanctions Act that seeks to prevent foreign investment in Iran's energy sector. Other legislation, such as H.R. 1357, H.R. 2347 (passed by the House), and S.1430, promote divestment of companies that do business with Iran. Some in the Administration believe that only a change of Iran's regime would end the threat posed by Iran. On October 21, 2007, the Administration named several Revolutionary Guard entities and personalities as proliferators and supporters of terrorism, and the Guard's 'Qods Force' as a terrorism supporter (but not as a foreign terrorist organization, FTO)."
CRS Report for Congress, RL32048