"The United States has been a leader of worldwide efforts to prevent the spread of nuclear weapons. To this end, the international community and many individual states have agreed to a range of treaties, laws, and agreements, known collectively as the nuclear nonproliferation regime, aimed at keeping nations that do not have nuclear weapons from acquiring them. The nonproliferation regime has also been concerned with preventing terrorists from obtaining a nuclear weapon or the materials to craft one. The attacks on New York and Washington September 11, 2001, added a new level of reality to the threat that terrorists might acquire a nuclear weapon and explode it in a populated area. Other nonproliferation concerns include a number of regional crisis points. In the Middle East, the possibility that Iraq has resumed, or may resume, its nuclear weapons program is a major concern driving the U.S. campaign against Saddam Hussein's regime. Iran's nuclear weapons development is also a threat, with recently released satellite evidence indicating that it is constructing uranium enrichment and heavy water production facilities. North Korea's acknowledgment that it is developing uranium enrichment capability, and moves to restart its plutonium production reactor, have enhanced the danger of nuclear proliferation there. The India-Pakistan nuclear arms race makes the continuing confrontation between those two countries particularly sensitive. There is concern about China's actions in expanding its nuclear force, and of Chinese and Russian activities that may encourage proliferation in the other regions."
CRS Issue Brief for Congress, IB10091