The United States has accused China of secretly carrying out at least one yield-producing nuclear test in recent years, a claim that, if substantiated, would mark a dramatic breach of Beijing’s long-stated moratorium on such activities and further destabilize an already fragile global arms control system. The allegation, revealed this week by a senior U.S. official, comes at a moment of heightened nuclear tension following the expiration of the New START treaty with Russia and renewed debate in Washington about resuming American nuclear testing.
Speaking at the Conference on Disarmament in Geneva, Under Secretary of State for Arms Control and International Security Thomas DiNanno said the U.S. government believes China has conducted nuclear explosive tests with yields in the hundreds of tons, while actively concealing those activities. According to DiNanno, China’s People’s Liberation Army deliberately sought to obscure the tests, recognizing that they would violate test ban commitments. He specifically alleged that one such yield-producing nuclear test took place on June 22, 2020.
The claims, first reported and analyzed in detail by The War Zone, immediately raised questions about how such testing could have occurred without broader international detection and why U.S. intelligence assessments on the matter appear to diverge from other official reports. At the time of DiNanno’s remarks, the U.S. government had not released additional evidence or technical details to support the allegation, nor clarified when American officials reached their conclusions.
China is a signatory to the Comprehensive Nuclear-Test-Ban Treaty, though it has never ratified the agreement. The United States is in the same position. Both countries maintain self-imposed moratoriums on yield-producing nuclear tests, while continuing to conduct sub-critical experiments that do not involve a full nuclear chain reaction and are permitted under the treaty framework. China’s last acknowledged full-scale nuclear test occurred in 1996, while the United States last conducted one in 1992.
DiNanno alleged that China used a technique known as decoupling to reduce the seismic signals generated by an underground nuclear explosion, making it harder for the global monitoring system to detect. The Comprehensive Nuclear-Test-Ban Treaty relies primarily on a worldwide network of hundreds of seismic stations designed to identify the telltale vibrations associated with nuclear detonations. Decoupling, if successful, could significantly blunt the effectiveness of that system for lower-yield tests.
Historically, nuclear testing has sharply declined since the end of the Cold War. Russia’s last official nuclear test took place in 1990, just before the collapse of the Soviet Union. The United Kingdom, France, India, and Pakistan all conducted yield-producing tests in the 1990s, while North Korea remains the only country known to have tested nuclear weapons in the 21st century, detonating devices between 2006 and 2017. Against that backdrop, allegations of clandestine testing by a major nuclear power carry profound strategic implications.
What complicates the U.S. accusation is the absence of corroboration in other American government publications. The State Department’s most recent arms control compliance report, released in April 2025, made no mention of Chinese yield-producing nuclear tests. That report did reiterate longstanding U.S. claims that Russia has engaged in supercritical testing, accusations Moscow denies. Likewise, the Pentagon’s December 2025 report on Chinese military developments did not reference nuclear testing activity.
The timing of the alleged 2020 test overlaps with earlier U.S. concerns about activity at China’s Lop Nur nuclear test site. A State Department compliance report published in June 2020 cited extensive excavation, the use of explosive containment chambers, and interruptions in data transmission from international monitoring stations as reasons for concern about China’s adherence to a “zero-yield” standard. DiNanno’s allegation that a yield-producing test occurred that same month adds a new layer of significance to those earlier observations.
China has forcefully rejected the accusation. Following DiNanno’s speech, Chinese Ambassador Shen Jian told reporters that Beijing firmly opposes what he described as false narratives about a so-called China nuclear threat, arguing that the United States is responsible for exacerbating the arms race. Chinese officials have repeatedly reiterated their commitment to a testing moratorium and accused Washington of using unproven claims to justify its own strategic ambitions.
The dispute unfolds amid a dramatic expansion of China’s nuclear forces. U.S. assessments indicate that Beijing currently possesses around 600 nuclear warheads, a number projected to rise to 1,000 by 2030 and as many as 1,500 by 2035. Satellite imagery and intelligence reports have documented the construction of vast new missile silo fields, advances in mobile and sea-based delivery systems, and work on nuclear-capable hypersonic glide vehicles. While still smaller than the arsenals of the United States and Russia, which each hold roughly 4,000 warheads, China’s buildup is proceeding at a pace unseen in decades.
The allegations also intersect with the collapse of the existing arms control architecture. New START, the last remaining treaty limiting U.S. and Russian strategic nuclear forces, expired this week after a one-time extension. Although there are unconfirmed reports of interim, informal arrangements to maintain some limits, there is currently no binding framework governing the world’s two largest nuclear arsenals. Successive U.S. administrations have argued that any future agreement must include China, a position Beijing has consistently rebuffed.
President Donald Trump has repeatedly argued that existing treaties are outdated and inadequate. In comments last year and again this week, he suggested that the United States should consider nuclear testing on an “equal basis” with China and Russia, while calling for a new, modernized arms control agreement. Secretary of State and acting National Security Advisor Marco Rubio echoed that view, saying meaningful 21st-century arms control is impossible without China’s participation.
The question of whether the United States might resume yield-producing nuclear tests has become more urgent in light of DiNanno’s claims. While U.S. energy officials have previously downplayed the likelihood of such a move, DiNanno acknowledged widespread confusion about what the administration’s statements on testing actually mean. He stopped short of saying Washington plans to conduct new tests but emphasized a commitment to restoring what he called responsible behavior in nuclear testing.
The Comprehensive Nuclear-Test-Ban Treaty Organization weighed in following the Geneva remarks, adding further complexity. Executive Secretary Robert Floyd said the organization’s monitoring system is capable of detecting nuclear explosions with yields of roughly 500 tons of TNT or greater, but noted that no event consistent with a nuclear test was detected on June 22, 2020. Subsequent analyses, he said, did not change that assessment. Floyd stressed that any nuclear test explosion by any state would be of deepest concern and argued that bringing the test ban treaty fully into force is more urgent than ever.
As The War Zone has noted, the allegations raise unresolved questions about intelligence interpretation, detection limits, and political signaling at a time when nuclear guardrails are eroding. Whether more evidence emerges or the claims remain contested, the episode underscores how quickly decades of relative restraint around nuclear testing could give way to renewed suspicion, competition, and potentially, a dangerous new chapter in the global arms race.
