Diplomatic tensions flared this week as the United States publicly accused China of conducting a covert nuclear test in 2020, a claim swiftly denied by Beijing and dismissed by international nuclear watchdogs. The controversy erupted on Friday, February 6, 2026, during a high-stakes United Nations disarmament conference in Geneva, Switzerland, just days after the expiration of a key nuclear arms-control treaty with Russia.
At the center of the storm is Thomas DiNanno, the US Under Secretary of State for Arms Control and International Security, who leveled the explosive allegation that China had carried out a yield-producing nuclear test on June 22, 2020. According to Reuters, DiNanno asserted before delegates, “I can reveal that the US government is aware that China has conducted nuclear explosive tests, including preparing for tests with designated yields in the hundreds of tonnes.” He further claimed that China’s military “sought to conceal testing by obfuscating the nuclear explosions because it recognised these tests violate test ban commitments.”
DiNanno’s remarks did not end at the conference podium. He took to social media to amplify his message, arguing for what he called “new architecture” in nuclear weapons control agreements. He pointed to the expiration of the New START treaty with Russia as a watershed moment, stating, “New START was signed in 2010 and its limits on warheads and launchers are no longer relevant in 2026 when one nuclear power is expanding its arsenal at a scale and pace not seen in over half a century and another continues to maintain and develop a vast range of nuclear systems unconstrained by New START’s terms.”
The timing of these accusations is no coincidence. The New START treaty, a cornerstone of nuclear arms control between the US and Russia, expired in early February 2026. This has left a vacuum in the global arms control regime, fueling anxieties about an emerging nuclear arms race. Russia, for its part, withdrew its ratification of the Comprehensive Nuclear Test Ban Treaty (CTBT) in 2023, further muddying the waters.
In the wake of the US allegations, the international response was swift and pointed. Robert Floyd, executive secretary of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), issued a statement on February 7, 2026, seeking to calm the waters. “The body’s monitoring system did not detect any event consistent with the characteristics of a nuclear weapon test explosion at the time of the alleged Chinese test,” Floyd said, according to Reuters. He added that this assessment remained unchanged even after further detailed analyses of the data.
China’s response was equally unequivocal. At the Geneva conference, Shen Jian, China’s ambassador on nuclear disarmament, rejected the US accusations outright. “We firmly oppose this false narrative and reject the US’s unfounded accusations,” Shen said. He went on to argue that “the US’s series of negative actions in the field of nuclear arms control are the biggest source of risk to international security.” Later, Shen reiterated on social media, “China has always honored its commitment to the moratorium on nuclear testing.”
Diplomats in attendance at the conference described the US allegations as both new and concerning, with some expressing surprise at the timing and tone of the accusations. The issue of nuclear testing has long been a flashpoint in international relations, with the CTBT serving as a key—if imperfect—barrier to the resumption of nuclear explosions by major powers. Both China and the US have signed but not ratified the CTBT, while Russia had both signed and ratified the treaty before its withdrawal in 2023.
The broader context is one of mounting distrust and shifting power dynamics. According to The Washington Post, the US top nuclear arms official argued that “recent secretive underground tests by China and Russia have given Washington reason to conduct ‘parallel steps’ as a decades-long moratorium on nuclear testing among major powers is unraveling.” This sentiment was echoed by President Donald Trump, who has previously instructed the US military to prepare for the resumption of nuclear tests. On October 31, 2025, Trump declared that Washington would begin testing nuclear weapons “on an equal basis” with Moscow and Beijing, though he did not elaborate on the specifics of these potential tests.
The implications of these developments are profound. The expiration of the New START treaty and the unraveling of the CTBT framework threaten to upend decades of painstaking progress in nuclear arms control. For many observers, the current moment feels eerily reminiscent of the Cold War, when suspicion and brinkmanship dominated the global stage. The US’s push for a new era of arms control agreements, one that would include China as a full participant, has so far met with little enthusiasm from Beijing, which remains wary of what it sees as attempts to constrain its strategic capabilities.
Meanwhile, the CTBTO’s robust global monitoring network—which includes seismic, hydroacoustic, and infrasound sensors—remains the world’s best line of defense against clandestine nuclear tests. The organization’s assurance that no evidence supports the US claim is a critical counterpoint to the escalating rhetoric. Yet, as history has shown, the absence of evidence is not always enough to quell suspicion—especially when great power rivalry is at play.
For the broader international community, the stakes could not be higher. A return to nuclear testing by any major power would almost certainly trigger a cascade of similar actions, undermining decades of nonproliferation efforts and increasing the risk of miscalculation or accidental escalation. As the world watches, the question remains: can diplomacy and verification mechanisms hold the line, or are we on the cusp of a new nuclear age?
In the end, the clash over China’s alleged nuclear test is about more than just one explosion or one accusation. It is a test of the global arms control system itself—and of the ability of nations to navigate an increasingly complex and dangerous world without repeating the mistakes of the past.