A decade after the U.S. Senate declined to ratify the Comprehensive Test Ban Treaty (CTBT), President Barack Obama is preparing an effort to reverse that decision. But to secure Senate backing this time around, the Obama administration must first overcome residual concerns among some senators that the treaty will harm U.S. national security.
The CTBT prohibits all nuclear explosions, whether for military or other purposes, in any environment. Its practical effect would be to extend test prohibitions contained in current treaties and agreements to include underground testing of all nuclear explosive devices, the last domain not formally prohibited by existing bans.
As of October 2009, 182 national governments (out of 195 possible signatories) have signed the CTBT, and 150 countries have deposited their instruments of ratification with the U.N. secretary-general. These totals give the CTBT a larger potential membership than most international arms control agreements.