"The Bush Administration has pursued several avenues to attempt to contain or end the potential threat posed by Iran, at times pursuing limited engagement, and at other times leaning toward pursuing efforts to change Iran's regime. Some experts believe a potential crisis is looming over Iran's nuclear program because the Bush Administration is skeptical that efforts by several European allies to prevent a nuclear breakout by Iran will succeed, although the Administration announced steps in March 2005 to support those talks. Some advocate military action against Iran's nuclear infrastructure, but others believe that a combination of diplomatic and economic rewards and punishment are the only viable options on the nuclear issue. U.S. sanctions currently in effect ban or strictly limit U.S. trade, aid, and investment in Iran and penalize foreign firms that invest in Iran's energy sector, but unilateral U.S. sanctions do not appear to have materially slowed Iran's WMD programs to date."
CRS Report for Congress, RL32048