"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 continues, generated primarily by Iran's nuclear program and intensified by Iran's military assistance to armed groups in Iraq and Afghanistan and to Lebanese Hezbollah. In part to direct regional attention to that view but also to engage Iran on an Iraq solution, the Administration attended regional conferences on Iraq on March 10, 2007, and May 3-4, 2007, both attended by Iran (and Syria), and subsequently has held a series of bilateral meetings with Iran in Baghdad. […] To strengthen its diplomacy, the Administration has maintained a substantial naval presence in the Persian Gulf and has been arresting Iranian agents in Iraq. The Administration strongly denies the widespread speculation that it plans military action against Iran, but has refused to rule it out. Some legislation passed in the 110th Congress, including H.R. 140 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, 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."
CRS Report for Congress, RL32048