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Pillar 1

Action 10

All nuclear-weapon States undertake to ratify the Comprehensive Nuclear-Test-Ban Treaty with all expediency, noting that positive decisions by nuclear-weapon States would have the beneficial impact towards the ratification of that Treaty, and that nuclear-weapon States have the special responsibility to encourage Annex 2 countries, in particular those which have not acceded to the Treaty on the Non-Proliferation of Nuclear Weapons and continue to operate unsafeguarded nuclear facilities, to sign and ratify.

United Kingdom

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What has the NWS done so far (prior to the current Review Cycle)?

The UK (with France) became the first NPT nuclear-weapon states to ratify the CTBT on 6 April 1998 and it has maintained its moratorium on nuclear testing since.

The UK is one of the largest financial contributors to the Comprehensive Test Ban Treaty Organization (CTBTO), providing £4.5 million annually. The UK maintains the United Kingdom National Data Centre and hosts 13 facilities spread across the UK and Overseas Territories, which support the International Monitoring System. These include 11 monitoring stations (either infrasound, hydroacoustic or radionuclide), an auxiliary seismic array and a radionuclide laboratory. These facilities are backed up by research through the Atomic Weapons Establishment forensic seismology and radionuclide team.

The UK provides technical experts, R&D and training and UK specialists contribute to CTBTO working groups and scientific development (e.g., seismic forensics at AWE Blacknest, radionuclide detection methods at GBL15).

The UK has consistently pushed for the treaty’s entry into force and hosted a P5 Experts Meeting on nuclear disarmament verification and the CTBT in April 2012. The P5 has called upon all states to uphold their national moratoria on nuclear weapons test explosions or any other nuclear explosions, and to refrain from acts that would defeat the object and purpose of the Treaty pending its entry into force.

At the 2015 Conference on the Entry into Force of the CTBT, Foreign Office Minister Alistair Burt stated that “Promoting Entry into Force of the CTBT is one of the United Kingdom’s key disarmament and non-proliferation priorities. The UK strongly supports the continued development of the Treaty’s global verification regime.”

What is the NWS doing on this action in the current Review Cycle?

The UK stated at the High-Level Segment of the Conference on Disarmament in 2024 that the CTBT is an "essential treaty” and a “fundamental instrument that contributes to international security and disarmament.

The UK stated in its 2025 report to the NPT that the CTBT and its entry into force are “a vital part of the step-by-step approach to nuclear disarmament. The UK continues to be a vocal campaigner, including by regularly lobbying states to sign and ratify.”

The UK has continued to be one of the largest financial contributors to the CTBTO, continuing to provide extensive technical and administrative support and to maintain the UK National Data Centre and thirteen facilities spread across the world that support the International Monitoring System.

Sources

  • Comprehensive Test Ban Treaty Organization (CTBTO). Station Profiles. https://www.ctbto.org/our-work/station-profiles
  • Foreign and Commonwealth Office. Draft National Report Pursuant to Actions 20 and 21 of the Nuclear Non-Proliferation Treaty (NPT) 2010 Review Conference Final Document (London), 11 March 2025.
  • Foreign and Commonwealth Office. National report of the United Kingdom of Great Britain and Northern Ireland pursuant to actions 5, 20 and 21 of the action plan of the 2010 Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons for the tenth Review Conference of the Parties to the Treaty (London), 5 November 2022.
  • Atomic Weapons Establishment. Comprehensive Nuclear Test Ban Treaty Monitoring. https://www.awe.co.uk/what-we-do/national-security/comprehensive-test-ban-treaty-monitoring/
  • Hansard. House of Commons. Written Statement, 21 May 2013. Column 71WS. https://hansard.parliament.uk/Commons/2013-05-21/debates/13052150000027/NuclearDisarmamentAndNon-Proliferation
  • Alistair Burt. UK Ministerial intervention by Foreign Office Minister Alistair Burt on the Comprehensive Nuclear-Test-Ban Treaty (CTBT) Article XIV Conference Entry into. 23 September 2011. https://www.ctbto.org/sites/default/files/2022-07/uk_2011.pdf

United States

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What has the NWS done so far (prior to the current Review Cycle)?

During his 2009 “Prague Speech,” President Obama announced that the United States would “immediately and aggressively” pursue U.S. ratification of the Comprehensive Nuclear Test Ban Treaty, and enshrined it as a key priority for his administration’s non-proliferation agenda. That same year, Secretary of State Clinton attended the CTBT Article XIV Conference––the first time in nearly a decade that the United States had participated at the conference at that level of representation––and emphasized that “we will work in the months ahead both to seek the advice and consent of the United States Senate to ratify the treaty, and to secure ratification by others so that the treaty can enter into force.” Ultimately, the Obama administration was unsuccessful in securing ratification during its tenure.

The Trump administration reversed its predecessor’s policies with respect to the CTBT. In its 2018 Nuclear Posture Review, the Trump administration explicitly stated that it “will not seek ratification of the Comprehensive Nuclear Test Ban Treaty.” [3] It did note, however, that it would “not resume nuclear explosive testing unless necessary to ensure the safety and effectiveness of the U.S. nuclear arsenal, and call[ed] on all states possessing nuclear weapons to declare or maintain a moratorium on nuclear testing.”

Throughout this period, the United States extensively supported the development of the CTBT’s on-site inspection protocols and detection capabilities to create the ultimate conditions for universal ratification and entry into force. In a demonstration of support for the spirit of the treaty, the United States attended the International Day Against Nuclear Testing event hosted by Kazakhstan and the CTBT Article XIV Conference in 2021.

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What is the NWS doing on this action in the current Review Cycle?

As it has done since 1992, the United States has continued to abide by its moratorium on nuclear weapons test explosions or any other nuclear explosions. In addition, during her tenure the Biden administration’s NNSA Administrator reiterated on multiple occasions that there was no technical need for the United States to resume nuclear testing. [6] In a demonstration of transparency, in 2022 and 2023 journalists and civil society experts were invited to tour the Nevada National Security Site to view the United States’ stockpile stewardship capabilities, and representatives from NPT States parties were invited to Sandia National Laboratories and Los Alamos National Laboratory for transparency visits.

The second Trump administration appears to be attempting to reverse these longstanding U.S. policy positions. In October and November 2025, President Trump made numerous statements indicating that he would begin the process of resuming U.S. nuclear testing. However, it remains unclear whether President Trump was referring to the actual testing of nuclear weapons or nuclear-capable delivery systems.

Sources

    • bama, Barack. Remarks by President Barack Obama in Prague, as delivered. Washington, DC: The White House, April 5, 2009. https://obamawhitehouse.archives.gov/the-press-office/remarks-president-barack-obama-prague-delivered
      Clinton, Hillary R. Remarks at CTBT Article XIV Conference. New York, NY: September 24, 2009. https://www.ctbto.org/sites/default/files/Documents/240909_US.pdf.
      U.S. Department of Defense. Nuclear Posture Review 2018. Washington, DC: Office of the Secretary of Defense, February 2018. https://fas.org/wp-content/uploads/media/2018-Nuclear-Posture-Review-Version-2.pdf.
      United States of America. "Actions 5, 20 and 21 of the Action Plan of the 2010 Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons: Report Submitted by the United States of America." NPT/CONF.2015/38. 2015 Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons, United Nations, New York, April 27–May 22, 2015. https://docs.un.org/en/NPT/CONF.2015/38.
      United States of America. "Actions 5, 20 and 21 of the Action Plan of the 2010 Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons: Report Submitted by the United States of America." NPT/CONF.2020/47. Tenth Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons, United Nations, New York, August 1–26, 2022. https://docs.un.org/en/NPT/CONF.2020/47.
      Kimball, Daryl G., and Carol Giacomo. "Managing an Arsenal Without Nuclear Testing: An Interview With Jill Hruby of the U.S. National Nuclear Security Administration." Arms Control Today, December 2023. https://www.armscontrol.org/act/2023-12/interviews/managing-arsenal-without-nuclear-testing-interview-jill-hruby-us-national.
      National Nuclear Security Administration. “Two NNSA National Labs host Nuclear Non-Proliferation Treaty representatives from around the world for transparency visit.” July 21, 2022. https://www.energy.gov/nnsa/articles/two-nnsa-national-labs-host-nuclear-non-proliferation-treaty-representatives-around.
      National Nuclear Security Administration. “NNSA demonstrates transparency during arms control and nonproliferation experts’ visit to Nevada.” December 1, 2023. https://www.energy.gov/nnsa/articles/nnsa-demonstrates-transparency-during-arms-control-and-nonproliferation-experts-visit.
      Brumfiel, Geoff. "Step Inside the Secret Lab Where America Tests Its Nukes." January 29, 2025, NPR, https://www.npr.org/2025/01/29/nx-s1-5276315/atomic-bomb-nuclear-weapons-lab-nevada.
      Trump, Donald (@realDonaldTrump). “The United States has more Nuclear Weapons than any other country. This was accomplished, including a complete update and renovation of existing weapons, during my First Term in office. Because of the tremendous destructive power, I HATED to do it, but had no choice! Russia is second, and China is a distant third, but will be even within 5 years. Because of other countries testing programs, I have instructed the Department of War to start testing our Nuclear Weapons on an equal basis. That process will begin immediately. Thank you for your attention to this matter! PRESIDENT DONALD J. TRUMP.” Truth Social, October 29, 2025. https://truthsocial.com/@realDonaldTrump/posts/115460423936412555.
    • ’Donnell, Norah. “President Trump on nuclear testing, the government shutdown, immigration, tariffs and U.S.-China relations.” CBS News, November 2, 2025. https://www.cbsnews.com/news/trump-on-nuclear-testing-government-shutdown-immigration-tariffs-china-60-minutes-transcript/.

France

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What has the NWS done so far (prior to the current Review Cycle)?

France definitively ended testing nuclear weapons in 1996. It signed the Comprehensive Nuclear-Test-Ban Treaty (CTBT) on 24 September 1996 and ratified it on 6 April 1998.

France expressed its support to efforts to universalise the CTBT, in particular among the Annex 2 States. Entry into force is a priority of its nuclear disarmament policy which has been recalled at the highest level (President Macron in 2020).

Its support is also materialised through EU work in support of the CTBTO. This support was formalised in Council Decision 2018/298 of February 2018.

What is the NWS doing on this action in the current Review Cycle?

France has continued to support politically the objective of the entry into force of the CTBT and to speak in favour of its universalisation.

In 2023, it issued a statement regretting Russia's decision to "de-ratify" the CTBT.

Sources

National Report submitted by France. Report submitted by France under actions 5, 20 and 21 of the Final Document of the 2010 Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons (2022–2026). NPT/CONF.2026/PC.III/2. 7 March 2025, https://docs.un.org/en/NPT/CONF.2026/PC.III/2

Emmanuel Macron. Speech of the President of the Republic on the Defense and Deterrence Strategy. (Paris), 7 February 2020. https://www.elysee.fr/en/emmanuel-macron/2020/02/07/speech-of-the-president-of-the-republic-on-the-defense-and-deterrence-strategy

France Diplomacy. Traité sur l’interdiction complète des essais nucléaires (TICE) – La France déplore la décision de la Russie de révoquer sa ratification du traité. [Comprehensive Nuclear-Test-Ban Treaty (CTBT) – France deplores Russia's decision to revoke its ratification of the treaty] 2 November 2023. https://www.diplomatie.gouv.fr/fr/politique-etrangere-de-la-france/securite-desarmement-et-non-proliferation/actualites-et-evenements-lies-a-la-securite-au-desarmement-et-a-la-non/2023/article/traite-sur-l-interdiction-complete-des-essais-nucleaires-tice-la-france-deplore

France Diplomacy. Draft Joint Statement by France and the United Kingdom, on the occasion of the 25th anniversary of their ratification of the CTBT. 6 April 2023. https://www.diplomatie.gouv.fr/en/country-files/united-kingdom/news/article/draft-joint-statement-by-france-and-the-united-kingdom-on-the-occasion-of-the