The United States has accused China of conducting at least one yield-producing nuclear test in recent years, despite Beijing’s declared moratorium on such activity. The allegation was disclosed by senior U.S. officials during the Conference on Disarmament in Geneva, underscoring growing strain in global nuclear arms control frameworks.

Speaking at the conference, U.S. Under Secretary of State for Arms Control and International Security Thomas DiNanno stated that China’s People’s Liberation Army (PLA) had conducted nuclear explosive tests, including preparations for tests with yields in the hundreds of tons range. The remarks come amid heightened concern over China’s rapid nuclear modernisation and the erosion of long-standing arms control arrangements.

“The PLA sought to conceal testing by obfuscating the nuclear explosions because it recognized these tests violate test ban commitments,” DiNanno said.

Allegations of Concealment and Decoupling Techniques

According to DiNanno, China employed decoupling techniques—methods intended to reduce seismic signatures and evade international monitoring systems—to obscure nuclear testing activity. He cited 22 June 2020 as the date of one such alleged yield-producing test.

China is a signatory to the Comprehensive Nuclear-Test-Ban Treaty (CTBT) but has not ratified it. Both Washington and Beijing maintain self-imposed moratoriums on yield-producing nuclear tests. China’s last publicly acknowledged nuclear test occurred in 1996, while the United States last conducted such testing in 1992.

CTBTO Technical Response

Following the U.S. claims, Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) Executive Secretary Robert Floyd issued a clarification regarding monitoring data.

Floyd stated that the CTBTO’s International Monitoring System (IMS)—a global network of hundreds of seismic stations—is capable of detecting nuclear test explosions with yields of approximately 500 tonnes of TNT or greater. He added that on 22 June 2020, the IMS did not detect any event consistent with a nuclear weapon test explosion.

While Floyd noted that mechanisms exist within the treaty framework to investigate smaller events, he emphasized that these tools can only be fully utilized once the CTBT enters into force.

Broader Context: China’s Nuclear Expansion

The allegations intersect with U.S. assessments of China’s expanding nuclear arsenal. According to U.S. intelligence estimates, China currently fields approximately 600 nuclear warheads, with projections of 1,000 by 2030 and 1,500 by 2035.

This buildup includes:

• Construction of large ICBM silo fields
• Development of nuclear-capable hypersonic glide vehicles
• Deployment of advanced delivery systems publicly displayed during China’s September 2025 military parade, including the DF-61 ICBM, JL-1 air-launched ballistic missile, and JL-3 submarine-launched ballistic missile

U.S. officials describe this as the most significant nuclear expansion by any power in decades, challenging the traditional U.S.–Russia-centric arms control paradigm.

Arms Control Vacuum After New START

The allegations arrive at a moment of structural uncertainty in nuclear arms control. The New START Treaty between the United States and Russia expired on 5 February 2026, leaving no legally binding limits on strategic nuclear forces.

DiNanno argued that bilateral frameworks are no longer sufficient, noting that New START’s parameters “are no longer relevant” in an environment where a third nuclear power is expanding its arsenal rapidly.

The Trump administration has repeatedly advocated for trilateral arms control negotiations involving the United States, Russia, and China. Beijing has consistently rejected such proposals, citing the disparity between its arsenal and the much larger U.S. and Russian stockpiles—estimated at roughly 4,000 warheads each, according to the Federation of American Scientists.

Prior U.S. Concerns and Chinese Response

U.S. concerns about Chinese nuclear testing are not new. The State Department’s June 2020 arms control compliance report cited activity at China’s Lop Nur nuclear test site, including year-round readiness, containment chambers, excavation work, and intermittent data disruptions affecting monitoring stations.

However, more recent U.S. government reports—including the State Department’s April 2025 compliance report and the Pentagon’s December 2025 China military power report—did not raise the issue of nuclear testing.

Responding to DiNanno’s remarks, China’s Deputy Permanent Representative in Geneva, Shen Jian, rejected the allegations, accusing Washington of exaggerating a “China nuclear threat” and asserting that the United States was itself driving arms race dynamics.

U.S. Nuclear Testing Policy Debate

The controversy also intersects with domestic U.S. debate over nuclear testing. In November 2025, President Donald Trump stated that the United States might resume nuclear testing “on an equal basis” with China and Russia, though subsequent statements by Energy Secretary Chris Wright suggested no imminent return to yield-producing tests.

DiNanno acknowledged uncertainty surrounding the administration’s position but emphasized U.S. intent to “restore responsible behavior” in nuclear testing. Experts note that resuming U.S. nuclear testing would require extensive preparation, including reactivating infrastructure at the Nevada Test Site—a process likely to take years.

Strategic Implications

If substantiated, the allegations carry several implications:

• Verification limits: Alleged low-yield testing highlights potential gaps in current monitoring regimes.
• Deterrence balance: Uneven adherence to moratoriums could affect confidence in stockpile reliability.
• Alliance reassurance: U.S. allies dependent on extended deterrence will closely track credibility implications.
• Arms race dynamics: Absent binding agreements, unconstrained expansion among major powers becomes more likely.

At present, the U.S. government has not released classified evidence supporting the claims, and further detail may emerge through congressional briefings or intelligence assessments.

Assessment

The U.S. accusations mark a notable escalation in nuclear-related rhetoric between Washington and Beijing at a time when formal arms control mechanisms are eroding. Whether the claims prompt policy shifts, renewed diplomatic engagement, or further strategic competition remains uncertain.

What is clear is that the episode underscores the growing difficulty of managing nuclear risk in a multipolar environment—where verification, transparency, and restraint are increasingly contested rather than assumed.