On February 17, 2026, the U.S. government unveiled new seismic data and intelligence that it claims support longstanding suspicions: that China secretly conducted a low-yield nuclear test at its Lop Nur site in June 2020. The disclosure, made at a Hudson Institute event in Washington, has reignited fierce debate over global nuclear arms control, the specter of a renewed arms race, and the fragile trust underpinning international treaties on nuclear testing.
According to Assistant Secretary of State for Arms Control and Nonproliferation Christopher Yeaw, a remote seismic station in Kazakhstan picked up a magnitude 2.75 seismic event on June 22, 2020. The event’s epicenter was about 450 miles from Lop Nur, the heart of China’s nuclear weapons program. "There is very little possibility that it is anything other than an explosion, a singular explosion," Yeaw asserted at the Hudson Institute, as reported by NPR. He went further, stating, "It is quite consistent with what you would expect from a nuclear explosive test."
Yet, the evidence is far from universally accepted. Independent experts, including Ben Dando of NORSAR, a Norwegian organization specializing in nuclear test monitoring, caution that the signal was weak and recorded at only a single station. Dando told NPR, "We can't really confirm or deny whether a nuclear test took place at this point." The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), whose global network detected the event, said two very small seismic events occurred 12 seconds apart. However, "with this data alone, it is not possible to assess the cause of these events with confidence," stated CTBTO Executive Secretary Robert Floyd, as reported by Reuters.
The Chinese government has categorically rejected the U.S. allegations. In a press conference last week, Chinese Foreign Ministry spokesperson Lin Jian called the accusations "completely groundless," adding, "China opposes the U.S.'s fabrication of pretexts for its own resumption of nuclear tests." In a written statement to Reuters, Chinese embassy spokesperson Liu Pengyu described the claims as "entirely unfounded" and accused the U.S. of "political manipulation aimed at pursuing nuclear hegemony and evading its own nuclear disarmament responsibilities." Liu urged the U.S. to "reaffirm the five nuclear-weapon states' commitment on refraining from nuclear tests, uphold the global consensus against nuclear tests, and take concrete steps to safeguard the international nuclear disarmament and non-proliferation regime."
The timing of the U.S. revelation is significant. The New START treaty, the last major arms limitation agreement between the U.S. and Russia, expired on February 5, 2026. President Donald Trump has publicly pressed China to join the U.S. and Russia in negotiating a replacement deal, but Beijing has so far refused, arguing its much smaller arsenal does not warrant inclusion. The U.S. claim of a secret Chinese test has become a rallying point for those in Washington advocating a return to American nuclear testing, with Trump himself using the allegations to justify such a move, according to The Washington Post.
Both the U.S. and China have signed the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which prohibits all nuclear explosions, but neither nation has ratified it. Under international law, they are still obligated to uphold the treaty’s terms. The U.S. last conducted an underground nuclear test in 1992 and has since relied on supercomputer simulations and sub-critical experiments—where small amounts of plutonium are exploded without triggering a nuclear chain reaction—to ensure the reliability of its arsenal. China’s last official test was in 1996, but, as Tong Zhao of the Carnegie Endowment for International Peace told NPR, satellite imagery shows significant expansion at Lop Nur, including new equipment areas, housing for personnel, and at least one new tunnel.
Details about the alleged 2020 test remain murky. Yeaw suggested that China used a technique known as "decoupling," detonating the device inside a large underground cavity to muffle the seismic signature and obscure the true yield. He declined to specify the estimated yield but said the event was "yield-producing," meaning it triggered a runaway nuclear chain reaction. Dando noted that a magnitude 2.75 event could correspond to an explosion equivalent to tens of tons of TNT, but with decoupling, a much larger blast could be concealed. The CTBTO’s Floyd confirmed that the seismic events were "far below" the detection threshold for nuclear explosions of 551 tons of TNT or more, further muddying the waters.
Why would China risk such a clandestine test? Experts point to several possible motivations. With only 45 nuclear tests conducted before the global moratorium, China lacks the extensive test data that the U.S. or Russia possess. As a result, each additional test could yield disproportionately valuable information for Chinese weapons designers. Zhao suggested China might be investigating lower-yield warheads for limited conflict scenarios or testing new designs for delivery systems such as hypersonic missiles. Yeaw hinted at broader strategic aims: "We do know that nations don't take these risks … without an expectation of significant gain."
Meanwhile, the scale of China’s nuclear build-up is drawing increasing scrutiny. The Pentagon estimates that China now possesses over 600 operational warheads—up from about 200 in 2019—and is on track to exceed 1,000 by 2030, approaching parity with the U.S. and Russia. This rapid expansion, coupled with alleged testing activity, has intensified American concerns about strategic stability and the future of arms control.
For its part, China maintains that it is in compliance with its international obligations and accuses the U.S. of hypocrisy. Beijing has repeatedly pointed out that Washington, too, has not ratified the CTBT and continues to invest billions in modernizing its nuclear arsenal. The U.S. argues that its activities, which include sub-critical tests and advanced simulations, do not violate the testing ban.
Independent analysts remain cautious. While the U.S. intelligence community appears convinced by the seismic data and possible classified evidence, the international monitoring regime has not reached a definitive conclusion. As Dando told NPR, "I would not say that there's really strong conclusive evidence." The CTBTO echoed this, stating that "with this data alone, it is not possible to assess the cause of these events with confidence."
As the debate rages, the stakes are high. The expiration of New START and the absence of a new arms control framework have raised fears of a new nuclear arms race. The U.S. is currently weighing options, including adding more warheads to its missiles, bombers, and submarines. Yeaw acknowledged the Pentagon is considering "a bunch of options" and expressed hope for renewed negotiations with both China and Russia.
For now, the world is left with more questions than answers. Was the seismic event at Lop Nur in 2020 a clandestine nuclear test, or simply a natural tremor? The international community’s ability to monitor and enforce nuclear agreements is being put to the test, even as the geopolitical rivalry between the world’s major powers intensifies. What happens next could shape the course of nuclear policy for years to come.