How Effective Are U.S. Sanctions on Iran？

Iran＇s nuclear development has become a serious threat to the U.S.-led nuclear nonproliferation movement. It also threatens Israel and other U.S.allies in the Middle East. It is one of the U.S.＇ biggest problems in the area. The U.S. ratcheted up sanctions on Iran after 2003 as the nuclear issue grew more urgent. Iran has responded with its own policies.