"The Bush Administration characterizes Iran as a 'profound threat to U.S. national security interests.' The Administration perception is generated primarily by Iran's nuclear program but is increasingly focused on Iran's military assistance to armed groups in Iraq, which is resulting in U.S. battlefield losses. Iranian aid to the Palestinian group Hamas and Lebanese Hezbollah is also considered a key threat to U.S. interests. 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, although Administration officials say that this finding was not the main thrust of the NIE, which judged Iran to be continuing uranium enrichment. 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 end its enrichment of uranium. […] To strengthen its diplomacy, the Administration has maintained a substantial naval presence in the Persian Gulf. The Administration has strongly denied 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 believe that the Administration might take military action to curb Iran's 'malign' influence in Iraq. Others believe that only a change of Iran's regime would end the threat posed by Iran, although regime change is not currently a prominent feature of Administration policy toward Iran."
CRS Report for Congress, RL32048