For decades, a global ban on nuclear test explosions has been a central goal, and is now a central element, of the nuclear nonproliferation and disarmament regime because an effective, comprehensive, verifiable test ban directly constrains the ability of all parties to develop new or more-advanced nuclear weapons. But the 1996 Comprehensive Test Ban Treaty and the de facto global nuclear test moratorium the it helped establish are now facing unprecedented new challenges.
May 2026
By Daryl G. Kimball
For decades, a global ban on nuclear test explosions has been a central goal, and is now a central element, of the nuclear nonproliferation and disarmament regime because an effective, comprehensive, verifiable test ban directly constrains the ability of all parties to develop new or more-advanced nuclear weapons.
The push to end all nuclear test explosions has also been driven by the widespread human suffering and environmental contamination produced by more than 2,000 atmospheric and underground nuclear test explosions since 1945, the effects of which continue to affect downwind populations today.
Three decades after the conclusion of the 1996 Comprehensive Test Ban Treaty (CTBT), it has 187 signatures and near-universal support, but the treaty and the de facto global nuclear test moratorium are facing unprecedented new challenges. Not only have nine key states failed to ratify it, but there are new U.S. accusations of noncompliance against China and Russia, and President Donald Trump has threatened to resume U.S. nuclear testing for the first time since 1992.
The situation requires that all states parties urgently reaffirm the value of the CTBT and call for new measures to ensure compliance at this month’s nuclear Nonproliferation Treaty Review Conference and beyond.
Although the CTBT Organization’s International Monitoring System is more effective than originally envisioned, very low-yield nuclear test explosions can still be difficult to detect without short-notice, on-site inspections, which will only be available once the treaty enters into force.
This is why, some 20 years ago, civil society experts recommended that the “nuclear weapon states should implement confidence-building … measures at their sites” to ensure they are not currently engaged in prohibited activities. It is also why in 2023, the head of the U.S. National Nuclear Security Administration (NNSA), Jill Hruby, suggested that the United States, Russia, and China, could work together “to develop a regime that would allow reciprocal observation with radiation detection equipment at each other’s subcritical experiments to allow confirmation that the experiment was consistent with the CTBT.”
In the absence of the CTBT’s entry into force or new voluntary confidence-building measures, there remains risk that certain activities at these former nuclear testing sites that are prohibited—nuclear experiments that produce a self-sustaining nuclear chain reaction—might go undetected or might be misinterpreted as a nuclear explosive test.
This is the dangerous situation we are now facing.
Although U.S. nuclear weapons labs have confirmed year after year that there is no technical or military reason for renewed U.S. nuclear test explosions, on Oct. 30, 2025, Trump, threatened to resume nuclear testing “on an equal basis.” Since then, the White House and the NNSA have not been able or willing to clarify what kind of nuclear weapons tests Trump is talking about. In fact, the NNSA and U.S. Strategic Command have reaffirmed that there is no technical or military basis to restart nuclear explosive testing.
Nevertheless, an internal NNSA planning document from February indicates that the agency plans to “Execute the President’s directive with respect to the testing of the U.S. nuclear deterrent” before the end of 2028.
Trump’s impulsive directive to resume testing appears to be all about political retribution and his belief that some other nuclear-armed state has conducted a nuclear test in violation of a treaty that his administration does not support.
On February 6, a senior U.S. official alleged that China conducted a nuclear test explosion on June 22, 2020. U.S. officials also claim that data from a CTBTO primary seismic station in Kazakhstan shows that China conducted a 10-ton (TNT equivalent) nuclear test explosion. In 2019, Trump officials also claimed “Russia probably is not adhering to its nuclear testing moratorium in a manner consistent with the CTBT.”
However, the data available from the International Monitoring System and other seismic monitoring stations in the region do not indicate conclusively that the seismic events in China on June 22, 2020 were produced by a nuclear explosion, according to published statements from the CTBTO and respected nongovernmental scientific institutions. China and Russia have denied the U.S. allegations of nuclear testing.
Even if China conducted a clandestine nuclear test explosion in June 2020, or that Russia may have conducted such a test sometime after 1996, two nuclear wrongs don’t make a right.
Not only would further nuclear explosive testing by the United States (or others) violate the CTBT, but it would also undermine global security. Renewed U.S. explosive testing, at any yield, would set off a chain reaction of nuclear testing worldwide that would improve the nuclear capabilities of U.S. adversaries and blow apart the global nonproliferation system.
U.S. Assistant Secretary of State Christopher Yeaw stated Feb. 23 that he hoped the U.S. allegations would “spur a discussion on how we all approach responsible nuclear testing behavior going forward.” The only responsible nuclear testing behavior is not to do it and to take the steps necessary to detect and deter anyone else from doing so ever again.
This essay is based on a longer statement that is to be delivered to the 2026 NPT Review Conference on May 1.
By Daryl G. Kimball in Arms Control Today
As U.S. and Iranian negotiators consider returning to Islamabad for a second round of talks, it is clear that Washington and Tehran remain far apart on key nuclear issues.
Representatives from some 190 governments will convene beginning April 27 for the pivotal 11th Review Conference for the nuclear Nonproliferation Treaty (NPT) to assess progress toward implementation of the treaty's goals and objectives, view this release for critical resources and analysis before the conference.
Future of Nonproliferation Treaty on the Line at the 11th Review Conference
Resources and Analysis About the April 27-May 22 Meeting at the UN
For Immediate Release: April 16, 2026
Media Contacts: Daryl G. Kimball, Executive Director (202-463-8270 x107); Thomas Countryman, Chair of the Board and former Asst. Secretary of State for International Security and Nonproliferation and member of the U.S. NPT delegation in 2022 (via 202-463-8270 x104)
(Washington, D.C.)— Representatives from some 190 governments will convene beginning April 27 for the pivotal 11th nuclear Nonproliferation Treaty (NPT) Review Conference to assess progress toward implementation of the treaty's goals and objectives, reaffirm the consensus-based commitments made at the 1995, 2000, and 2010 Review Conferences, and negotiate an action plan to advance the treaty's core goals on nonproliferation, the peaceful use of nuclear technology under international safeguards, and disarmament.
The NPT Review Conference is held every five years. Unfortunately, the last two NPT Review Conferences (2015 and 2022) have failed to produce a consensus outcome document. The 2026 Conference President Du Hong Viet told Arms Control Today that another failure would further weaken the NPT. “We may lose the credibility of the NPT itself,” he warned.
Reaching agreement will be very difficult. The April 27-May 22 meeting will be held amid a multiplying array of challenges to this foundational treaty, which has been signed and ratified by 193 states. For example:
“Despite these strong crosswinds, NPT states can and must try to line up together behind the treaty and a set of core action steps to reduce the nuclear danger,” argues Daryl G. Kimball, executive director of the Arms Control Association, who has participated in every NPT Review Conference since 1995.
“Many NPT delegations will press for commitments from the five nuclear-armed states to close the 'disarmament deficit,'” he predicted. Each of the NPT's nuclear-armed states are in violation of the obligation to engage in ‘negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament’ as required by Article VI of the treaty.
“An outcome document will show to the world, our constituencies, our people, that they can still rely on the NPT for their security, and that they can be confident that governments are still working towards ensuring better security for all through these dialogues and discussions and sticking to the commitments that they have,” Viet told Arms Control Today in a March interview.
For the first time, the U.S. delegation will not be led by a Senate-confirmed ambassador with prior NPT experience. As a result, “effective leadership from the United States is, unfortunately, unlikely going into this Review Conference,” noted Kimball. “This will make it important for other states, particularly non-nuclear ‘middle powers,’ to provide the leadership and solutions necessary to move the NPT conference in the right direction.”
Ahead of this critical NPT Review conference, the Arms Control Association provides the following resources for reporters, journalists, and practitioners:
Additional, in-depth analysis from other leading experts is available in Arms Control Today:
The plenary session of the NPT Review Conference will be broadcast on UN TV.
For the official program of work, schedule, working papers and statements, see the Reaching Critical Will website at: https://reachingcriticalwill.org/disarmament-fora/npt/2026 Nongovernmental organizations will make presentations to the plenary on May 1.
