The contracting states to the Comprehensive Nuclear-Test-Ban Treaty (CTBT) are the states that have signed and ratified the international agreement banning all nuclear explosions in all environments. Technically they will not be "parties" until the treaty enters into force,^[1] at which point these states will also be Member States of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), which comes into existence upon entry into force of the treaty. Non-contracting states are also listed, including those that are signatories and those are not. States Signatories are Members of the CTBTO Preparatory Commission.

This article needs to be updated. (October 2023)

On September 24, 1996, the Comprehensive Nuclear-Test-Ban Treaty (CTBT) was opened for signature. All five nuclear weapons states recognized under the Nuclear Non-Proliferation Treaty (China, France, Russia, the United Kingdom, and the United States) signed the treaty, with 66 other states following that day.^[2] Fiji became the first state to ratify the treaty on October 10, 1996. As of March 2024, 187 states have signed and 178 states have ratified the treaty. Most recently, Papua New Guinea ratified the treaty in March 2024.^{[3][4][5][6][7]}

Signatures are received at the United Nations Headquarters in New York City by authorized representatives of the state.^[8] Ratification is achieved with the approval of either or both chamber of the legislature and executive of the state. The instrument of ratification serves as the document binding the state to the international treaty and can be accepted only with the validating signature of the head of state or other official with full powers to sign it.^[9] The instrument is deposited with the Secretary-General of the United Nations.^[10]

Under the CTBT, there are 195 Annex 1 states^[11] which include a subset of 44 Annex 2 states.^[12]

• Annex 1 states are agreed upon by conference and currently comprise all 193 United Nations member states, the Cook Islands, Holy See and Niue. All Annex 1 states may become members of the Executive Council, the principal decision-making body of the organization responsible for supervising its activities.^[13] These states are formally bound to the conditions of the treaty; however, their ratification is not necessary for the treaty to come into effect (unless they are also an Annex 2 state).
• Annex 2 states are those that formally participated in the 1996 Conference on Disarmament and possessed nuclear power or research reactors at the time.^[14] Annex 2 lists the following 44 States: Algeria, Argentina, Australia, Austria, Bangladesh, Belgium, Brazil, Bulgaria, Canada, Chile, China, Colombia, Democratic People's Republic of Korea, Democratic Republic of the Congo, Egypt, Finland, France, Germany, Hungary, India, Indonesia, Islamic Republic of Iran, Israel, Italy, Japan, Mexico, Netherlands, Norway, Pakistan, Peru, Poland, Republic of Korea, Romania, Russian Federation, Slovakia, South Africa, Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom, United States of America, and Vietnam.

Nine Annex 2 states have not ratified the treaty: China, Egypt, Iran, Israel, Russia and the United States have already signed the Treaty, whereas India, North Korea and Pakistan have not signed it. The treaty will come into force only with the signature and ratification of the above Annex 2 states of the treaty, 180 days after they have all deposited their instruments of ratification.^[15]

The following 9 states have signed but not ratified the treaty.

More information State, Annex ...

State[5][3]	Annex	Signed
China	21, 2	Sep 24, 1996
Egypt	21, 2	Oct 14, 1996
Iran	21, 2	Sep 24, 1996
Israel	21, 2	Sep 25, 1996
Nepal	1	Oct 8, 1996
Russia[lower-alpha 1]	21, 2	Sep 24, 1996
Somalia	1	Sep 8, 2023
United States	21, 2	Sep 24, 1996
Yemen	1	Sep 30, 1996

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Notes

The following 9 UN member states, in addition to the UN observer State of Palestine, have neither signed nor acceded to the treaty.

More information State, Annex ...

State	Annex
Bhutan	1
India	21, 2
Mauritius	1
North Korea	21, 2
Pakistan	21, 2
Saudi Arabia	1
South Sudan	1
Syria	1
Tonga	1

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India

In 1998, India said it would only sign the treaty if the United States presented a schedule for eliminating its nuclear stockpile, a condition the United States rejected.^[18]

Israel

In 2016, Israeli Prime Minister Benjamin Netanyahu said that its ratification was dependent upon "the regional context and the appropriate timing".^[19]

United States

The United States has signed the CTBT, but not ratified it; there is ongoing debate whether to ratify the CTBT.

The United States has stated that its ratification of the CTBT is conditional upon:

A: The conduct of a Science Based Stockpile Stewardship Program to ensure a high level of confidence in the safety and reliability of nuclear weapons in the active stockpile, including the conduct of a broad range of effective and continuing experimental programs.

B: The maintenance of modern nuclear laboratory facilities and programs in theoretical and exploratory nuclear technology which will attract, retain, and ensure the continued application of our human scientific resources to those programs on which continued progress in nuclear technology depends.

C: The maintenance of the basic capability to resume nuclear test activities prohibited by the CTBT should the United States cease to be bound to adhere to this treaty.

D: Continuation of a comprehensive research and development program to improve our treaty monitoring capabilities and operations.

E: The continuing development of a broad range of intelligence gathering and analytical capabilities and operations to ensure accurate and comprehensive information on worldwide nuclear arsenals, nuclear weapons development programs, and related nuclear programs.

F: The understanding that if the President of the United States is informed by the Secretary of Defense and the Secretary of Energy (DOE) – advised by the Nuclear Weapons Council, the Directors of DOE's nuclear weapons laboratories and the Commander of the U.S. Strategic Command – that a high level of confidence in the safety or reliability of a nuclear weapon type which the two Secretaries consider to be critical to the U.S. nuclear deterrent could no longer be certified, the President, in consultation with Congress, would be prepared to withdraw from the CTBT under the standard "supreme national interests" clause in order to conduct whatever testing might be required.^[20]

Proponents of ratification claim that it would:

1. Establish an international norm that would push other nuclear-capable countries like North Korea, Pakistan, and India to sign.
2. Constrain worldwide nuclear proliferation by vastly limiting a country's ability to make nuclear advancements that only testing can ensure.
3. Not compromise US national security because the Science Based Stockpile Stewardship Program serves as a means for maintaining current US nuclear capabilities without physical detonation.^[21]

Opponents of ratification claim that:

1. The treaty is unverifiable and that other nations could easily cheat.
2. The ability to enforce the treaty was dubious.
3. The U.S. nuclear stockpile would not be as safe or reliable in the absence of testing.
4. The benefit to nuclear nonproliferation was minimal.^[22]

On October 13, 1999, the United States Senate rejected ratification of the CTBT. During his 2008 presidential election campaign Barack Obama said that "As president, I will reach out to the Senate to secure the ratification of the CTBT at the earliest practical date."^[23] In his speech in Prague on April 5, 2009, he announced that "[To] achieve a global ban on nuclear testing, my administration will immediately and aggressively pursue U.S. ratification of the Comprehensive Test Ban Treaty. After more than five decades of talks, it is time for the testing of nuclear weapons to finally be banned."^[24]

An article in Bulletin of the Atomic Scientists describes how a North Korean underground nuclear test on May 25, 2009, was detected and the source located by GPS satellites. The authors suggest that the effectiveness of GPS satellites for detecting nuclear explosions enhances the ability to verify compliance with the Comprehensive Nuclear Test Ban Treaty, giving the United States more reason to ratify it.^[25]

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• List of parties to the Chemical Weapons Convention
• List of parties to the Convention on Certain Conventional Weapons
• List of parties to the Ottawa Treaty
• List of parties to the Partial Nuclear Test Ban Treaty
• List of parties to the Treaty on the Non-Proliferation of Nuclear Weapons
• List of parties to the Treaty on the Prohibition of Nuclear Weapons
• List of parties to weapons of mass destruction treaties