Allegations of clandestine nuclear testing have erupted onto the world stage, with the United States accusing China of violating long-standing moratoriums and nuclear test ban commitments. The controversy unfolded in Geneva at a United Nations disarmament conference on February 6, 2026, only days after the expiration of the New START nuclear treaty between the US and Russia—a development already stoking anxieties about an unraveling global arms-control regime. As these charges and countercharges ricocheted through diplomatic circles, an independent international monitor stepped forward to challenge Washington’s claims, adding yet another layer of complexity to an already fraught situation.
At the heart of the dispute is a statement by Thomas DiNanno, the US Under Secretary of State for Arms Control and International Security. According to Reuters, DiNanno told assembled delegates and the world’s press, "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 asserted that China’s military "sought to conceal testing by obfuscating the nuclear explosions because it recognised these tests violate test ban commitments." DiNanno went further, specifying, "China conducted one such yield-producing nuclear test on June 22 of 2020."
These are not idle words. DiNanno’s remarks—delivered both at the conference and amplified on social media—were pointed, suggesting not only that China had violated its obligations, but that the US was now compelled to rethink its own approach to nuclear arms control. As the Washington Post reported, the 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." The timing of these allegations was notable, coinciding with the expiration of the New START treaty, a cornerstone of US-Russian arms control since 2010.
DiNanno’s perspective was clear. As he put it in his social media posts, "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 implication: with old agreements lapsing and other powers allegedly acting in bad faith, the US may have little choice but to reconsider its own restraint.
But are these accusations grounded in fact? That’s where the plot thickens. Robert Floyd, executive secretary of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), quickly issued a statement intended to calm the waters. As Reuters reported, Floyd said on February 7, 2026, that the CTBTO’s sophisticated global 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 stressed that this assessment "remains unchanged after further detailed analyses." The CTBTO’s monitoring network, with its seismic, hydroacoustic, infrasound, and radionuclide sensors, is widely regarded as the gold standard for detecting nuclear explosions worldwide.
China, for its part, was quick to reject the US accusations. Shen Jian, China’s ambassador on nuclear disarmament, addressed the conference the following day, according to Reuters. While Shen did not directly respond to each of DiNanno’s charges, he did not mince words: "We firmly oppose this false narrative and reject the US’s unfounded accusations." He insisted, "China has always acted prudently and responsibly on nuclear issues," and later, on social media, stated flatly that "China has always honored its commitment to the moratorium on nuclear testing." Shen went further, turning the tables by suggesting that "the US’s series of negative actions in the field of nuclear arms control are the biggest source of risk to international security."
The diplomatic back-and-forth left many at the Geneva conference unsettled. As diplomats told Reuters, the US allegations were "new and concerning," raising the prospect that the world’s major nuclear powers could be drifting into a new era of mistrust and competition. The legal and political context only deepens the uncertainty. Both the US and China have signed the Comprehensive Nuclear Test Ban Treaty (CTBT), which prohibits all nuclear explosions, but neither has ratified it. Russia, in contrast, had signed and ratified the CTBT, but withdrew its ratification in 2023, further muddying the waters.
Against this backdrop, the US position on nuclear testing has also shifted. President Donald Trump, speaking on October 31, 2025, declared that Washington would start testing nuclear weapons "on an equal basis" with Moscow and Beijing, though he did not elaborate on what form that testing would take. Trump’s statement followed a pattern of expressing skepticism toward existing arms control frameworks, and he has previously argued that future nuclear treaties should include China—a proposal that Beijing has shown little interest in pursuing.
The international community, meanwhile, remains caught between these competing narratives. On one hand, the US points to a perceived erosion of norms and agreements, with DiNanno’s call for "new architecture" in nuclear weapons control reflecting a sense of urgency and frustration. On the other, China categorically denies any wrongdoing and casts the US as the destabilizing actor. The CTBTO, standing as an independent arbiter, finds no technical evidence to support the most incendiary of Washington’s claims.
What’s at stake is not just the credibility of individual governments, but the future of nuclear arms control itself. The expiration of the New START treaty in early February 2026 has left the world’s two largest nuclear arsenals without mutual limits for the first time in over a decade. The CTBT remains in limbo, unratified by key players and now openly questioned in its effectiveness and enforcement. The specter of a renewed nuclear arms race looms, with each side accusing the other of bad faith while insisting on its own rectitude.
For now, the world is left to weigh competing claims against the available evidence. The CTBTO’s monitoring data stands as a bulwark against rumor and suspicion, but the political pressures on all sides are mounting. As diplomats, scientists, and policymakers grapple with the implications, one thing is clear: the debate over nuclear testing, transparency, and trust is far from settled, and the stakes could not be higher.
In the end, while accusations and denials swirl, and the technical monitors hold their ground, the world watches—wondering if the fragile architecture of nuclear restraint can hold in the face of renewed suspicion and rivalry.