Cooperative Threat Reduction (CTR) programs refer to a series of collaborative efforts between the United States and the states of the former Soviet Union (especially Russia) to reduce the threat posed by the Soviet legacy of WMD. These programs are also known as "Nunn-Lugar Programs" after Senators Sam Nunn and Richard Lugar, who sponsored the first legislation to authorize them. The term is used here to cover all U.S. government programs in this area, including those administered by the Departments of Defense, Energy, and State. Only the Department of Defense uses the term "Cooperative Threat Reduction," however, in the names of its programs.

Recently the United States government has explored expanding nonproliferation assistance, including cooperative threat reduction programs, to states outside the former Soviet Union. The Nunn-Lugar Expansion Act permitted the Department of Defense to spend $50 million on cooperative threat reduction measures outside the former Soviet Union. The United States is funding the elimination of chemical weapons in Albania and Libya and the destruction CW production facilities in Yugoslavia. Other countries that may benefit from such expanded CTR programs include India, Pakistan, and North Korea.

While the United States has increased the number of countries that may benefit from CTR funding, it has also joined with other nations in the Global Partnership to increase international funding for CTR efforts.