"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 nuclear weapons or the materials to craft them. The attacks on New York and Washington of 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 focal points. North Korea's claim that it possesses nuclear weapons and is pursuing more has led to a diplomatic crisis. In the Middle East, Iran's nuclear weapons development remains a threat. Libya's voluntary revelation of its covert nuclear weapons program reinforced the fear that nations may develop weapons without being discovered. The continuing confrontation between India and Pakistan is made more dangerous by their possession of nuclear explosives. There is concern about Chinese and Russian activities that may encourage proliferation in the other regions."
CRS Issue Brief for Congress, IB10091