The Comprehensive Test Ban Treaty (CTBT)

The Comprehensive Test Ban Treaty CTBT obligates countries that sign and ratify the treaty "not to carry out any nuclear weapon test explosion or any other nuclear explosion."

Background. The 1963 Partial Test Ban Treaty banned nuclear tests in the atmosphere, underwater, and in outer space. This treaty did not prohibit underground nuclear testing, however. The CTBT bans nuclear tests in all environments, including underground.

Historically, the nuclear powers have relied heavily on nuclear testing to confirm the reliability and effectiveness of their arsenals and to develop new types of nuclear weapons. For decades, countries seeking to limit nuclear weapons have demanded a CTBT in the belief that such a treaty would limit the ability of the nuclear states to develop more powerful weapons and new types of nuclear arms. Indian Prime Minister Jawaharlal Nehru originally proposed a CTBT in 1954, but negotiations on the ban became feasible only after the end of the Cold War.

Countries concerned about nuclear proliferation, including the United States, supported a CTBT as a means of slowing the spread of nuclear arms to additional countries. They argued that although a country seeking to develop nuclear weapons might not need to conduct a test to build a simple fission (or atomic) bomb, such tests would be necessary if it sought to develop more complex and powerful thermonuclear (or hydrogen) bombs. Testing would also be necessary for a new nuclear country to develop small warheads for ballistic missiles.

At the 1995 Review and Extension Conference for the Nuclear Non-Proliferation Treaty (NPT), the member-states agreed to extend the NPT permanently but also endorsed a set of Principles and Objectives. One of these principles called for a CTBT to be negotiated and opened for signature by 1996. Negotiations on the CTBT that had already begun in the nuclear weapon states was a key factor in gaining the support of the non-nuclear weapon states for permanent extension of the NPT. States negotiated the CTBT in the Conference on Disarmament (CD).

The 1996 deadline for negotiating the CTBT was met, but only after heated debate on a number of issues. These issues included the question of whether the treaty should allow very small (low-threshold) nuclear tests or should ban all nuclear tests. A complete ban was agreed on. A second issue was whether the treaty should allow an exception for entry into force — whether the treaty should become legally binding after a certain number of states had ratified it or whether ratification by specific states would be required. The negotiators chose the second option.

Another obstacle to concluding the treaty was an Indian initiative calling on the nuclear weapon states to undertake a formal commitment to nuclear disarmament within a certain period of time. This condition was based on India's view that the CTBT as drafted was insufficient to achieve real progress in nuclear disarmament. Failing to gain support for its proposal, India blocked the consensus needed to move the treaty from the CD to the UN General Assembly. An Australian initiative overcame the Indian opposition and led to a resolution endorsing the treaty at a special session of the General Assembly. On September 24, 1996, the CTBT was opened for signature. As of September 2006, 176 states had signed the CTBT and 135 had ratified it. However, the treaty will not enter into force until 44 named nuclear-capable states (including the United States, India, Pakistan, and North Korea)  ratify the treaty; only 34 have done so.

Further Reading:

	PBS Frontline, Owen Cote, Jr., "A Primer on Fissile Material and Nuclear Weapons Design"
	CRS, Jonathan Medalia, "Nuclear Testing and Comprehensive Test Ban: Chronology Starting 1992"
	Arms Control Association, The Comprehensive Test Ban Treaty
	CRS, Jonathan Medalia, "Nuclear Weapons: Comprehensive Test Ban Treaty"
	CNS, Nuclear Non-Proliferation Treaty Resources
	NTI, Lawrence Sheinman, "The Comprehensive Test Ban Treaty"
	CNS, Inventory of International Organizations, CTBT
	U.S. State Department, CTBT Archive
	Comprehensive Test Ban Treaty Organization website