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). The Administration has indicated it wants to begin a CTBT "education" campaign with a goal of securing Senate advice and consent to ratification, but there have been no hearings on the treaty in the 111th or 112th Congresses. As of July 2012, 183 states had signed the CTBT and 157, including Russia, had ratified it. However, entry into force requires ratification by 44 states specified in the treaty, of which 41 had signed the treaty and 36 had ratified. Seven conferences have been held to facilitate entry into force, most recently on September 23, 2011.