"U.S. sanctions--and U.S. attempts to achieve imposition of multilateral and international sanctions on Iran--have been a significant component of U.S. Iran policy for several decades. In the 1980s and 1990s, U.S. sanctions were intended to try to compel Iran to cease supporting acts of terrorism and to limit Iran's strategic power in the Middle East more generally. Since the mid2000s, U.S. sanctions have focused on ensuring that Iran's nuclear program is for purely civilian uses and, since 2010, the international community has cooperated with a U.S.-led and U.N.authorized sanctions regime in pursuit of that goal. Still, sanctions against Iran have multiple objectives and address multiple perceived threats from Iran simultaneously."
CRS Report for Congress, RS20871
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html