Comprehensive Nuclear-Test-Ban Treaty: Background and Current Developments

Jonathan Medalia
Specialist in Nuclear Weapons Policy


A comprehensive nuclear-test-ban treaty (CTBT) is the oldest item on the nuclear arms control agenda. Three treaties currently bar all but underground tests with a maximum force equal to 150,000 tons of TNT. The Natural Resources Defense Council states the United States conducted 1,030 nuclear tests, the Soviet Union 715, the United Kingdom 45, France 210, and China 45. The last U.S. test was held in 1992; Russia claims it has not tested since 1990. In 1998, India and Pakistan announced several nuclear tests. Each declared a test moratorium; neither has signed the CTBT. North Korea conducted a nuclear test in 2006. 

Since 1997, the United States has held 23 "subcritical experiments" at the Nevada Test Site to study how plutonium behaves under pressures generated by explosives. It asserts these experiments do not violate the CTBT because they cannot produce a self-sustaining chain reaction. Russia reportedly held some since 1998. 

The U.N. General Assembly adopted the CTBT in 1996. As of January 6, 2010, 182 states had signed it; 151, including Russia, had ratified. Of the 44 that must ratify the treaty for it to enter into force, 41 had signed and 35 had ratified. Five conferences have been held to facilitate entry into force, most recently in 2009. 

In 1997, President Clinton sent the CTBT to the Senate. In October 1999, the Senate rejected it, 48 for, 51 against, 1 present. It is on the Senate Foreign Relations Committee's calendar. It would require a two-thirds Senate vote to send the treaty back to the President for disposal or to give advice and consent for ratification. In a speech in Prague in April 2009, President Obama said, "my administration will immediately and aggressively pursue U.S. ratification of the Comprehensive Test Ban Treaty." U.S. ratification would be followed by a diplomatic effort to secure ratification by the remaining states that must ratify for the treaty to enter into force. 

Past nuclear testing treaties have been accompanied by "safeguards," unilateral measures consistent with the treaties that the United States can take to buttress its nuclear intelligence and weapons. President Clinton conditioned his support for the CTBT on a package of safeguards, and President Obama said in his Prague speech, "As long as these weapons exist, the United States will maintain a safe, secure and effective arsenal to deter any adversary, and guarantee that defense to our allies." Thus, safeguards may accompany a future CTBT debate. 

Congress addresses nuclear weapon issues in the annual National Defense Authorization Act and the Energy and Water Development Appropriations Act. It considers the Stockpile Stewardship Program (listed as Weapons Activities), which seeks to maintain nuclear weapons without testing; the FY2010 appropriation is $6.384 billion. Congress considers a U.S. contribution to a global system to monitor possible nuclear tests. The FY2010 appropriation is $30.0 million. 

This report will be updated. For a detailed presentation of pros and cons, see CRS Report RL34394, Comprehensive Nuclear-Test-Ban Treaty: Issues and Arguments, by Jonathan Medalia. For a discussion of safeguards and the CTBT, see CRS Report R40612, Comprehensive Nuclear- Test-Ban Treaty: Updated "Safeguards" and Net Assessments, by Jonathan Medalia.


Date of Report: January 6, 2010
Number of Pages: 49
Order Number: RL33548
Price: $29.95

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