The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a legally binding global ban on nuclear explosive testing and the final step in the vision laid out fifty years ago by President John F. Kennedy. The CTBT was opened for signature in 1996.

Since 1992, the United States has observed a unilateral moratorium on nuclear explosive testing. This moratorium is based on our national security assessment that the United States does not need to conduct nuclear explosive tests in order to ensure the safety, security and effectiveness of the nuclear forces we maintain to deter nuclear attacks on the United States, our allies and partners. Moreover, reinforcing the international norm against nuclear explosive testing is very much in the U.S. security interest.

Entry into force of the Comprehensive Test Ban (CTBT) would create a legally binding prohibition on nuclear explosive tests for all of its parties. The CTBT will:

• Hinder states that do not have nuclear weapons expertise and experience from advancing their nuclear weapons capabilities, while not affecting the ability of the United States to maintain its own nuclear deterrent force. States interested in pursuing a nuclear weapons program or advancing or expanding the capabilities of an existing nuclear weapons program would have to either risk deploying weapons without confidence that they will work as designed, or incurring international condemnation and reprisals by conducting nuclear explosive tests in violation of the Treaty;
• Impede states with more established nuclear weapon capabilities from confirming the performance of advanced nuclear weapon designs that they have not tested successfully in the past; and
• Constrain regional arms races in the years and decades to come. These constraints will be particularly important in Asia, where states are building up and modernizing nuclear forces.