Link: http://www.thereaganvision.org/wp-content/uploads/2011/08/CRS-Comprehensive-Nuclear-Test-Ban-Treaty-Background-and-Current-Developments.pdf

From the Congressional Research Service via The Reagan Vision -

"A ban on all nuclear tests is the oldest item on the nuclear arms control agenda. Three treaties that entered into force between 1963 and 1990 limit but do not ban such tests. In 1996, the U.N. General Assembly adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which would ban all nuclear explosions. In 1997, President Clinton sent the CTBT to the Senate, which rejected it in October 1999. 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.” However, the Administration focused its efforts in 2010 on securing Senate advice and consent to ratification of the New Strategic Arms Reduction Treaty (New START)."