China Denies U.S. Accusation of Nuclear Tests

U.S. claims of secret low-yield nuclear explosive tests by China are “outright lies,” Beijing said on February 9. Such tests would violate the informal global testing moratorium. The allegations are “completely groundless,” the nation’s foreign ministry said, and accused Washington of seeking pretexts to resume its own nuclear testing. 

On February 6, U.S. Under Secretary of State for Arms Control and International Security Thomas DiNanno told the UN Conference on Disarmament that China has conducted nuclear explosive tests — including one on June 22, 2020 — with yields “in the hundreds of tons,” using “decoupling” techniques to evade seismic detection and conceal test-ban violations. 

The accusation reflects Washington’s growing resolve to confront nuclear challenges from two near-peer adversaries, Russia and China, and signals possible adjustments or expansion of U.S. nuclear forces.

Accusation Follows Expiration of U.S.-Russia Nuclear Arms Control Treaty 

On February 5, with the expiration of New START — the last U.S.-Russia bilateral nuclear arms control treaty — President Donald Trump posted on Truth Social rejecting an informal extension. He called instead for negotiations on a “new, improved, and modernized” agreement, one he has long insisted must include China.

In recent years, Beijing has rapidly expanded its nuclear arsenal — from an estimated ~200 warheads in 2020 to more than 600 today, according to U.S. and independent assessments. U.S. projections indicate the stockpile could reach at least 1,000 nuclear warheads by 2030. China has consistently rejected trilateral arms control talks with the United States and Russia. 

Previous U.S. Concerns Over Beijing’s Secret Testing 

Although the 1996 Comprehensive Nuclear Test-Ban Treaty (CTBT) has never entered into force, the United States, Russia, and China — as signatories — have all pledged to observe a de facto moratorium on nuclear explosive testing, interpreted as “zero-yield,” or creating no sustained nuclear chain reaction. Nevertheless, the United States has repeatedly accused both China and Russia of low-yield violations.

In October 2025, President Trump alleged illicit nuclear explosive tests by China and Russia and called for the United States to resume similar testing for the first time since 1992. The State Department has cited concerns over Chinese yield-producing tests at China’s Lop Nur test site since at least 2019. Excavation activity suggested preparations for tests in underground caverns, employing “decoupling” techniques to muffle seismic signals and reduce detectability.

China insists its testing-related activities are focused solely on ensuring the reliability and safety of existing weapons. China conducted only 45 nuclear explosive tests before the 1996 moratorium — far fewer than the hundreds carried out by the United States and Soviet Union/Russia — and benefits from additional data. The United States relies primarily on supercomputer simulations for weapons design and stockpile stewardship. In 2015, Washington imposed sanctions on Chinese supercomputing entities for supporting simulated “nuclear explosion activities.”

U.S. Deterrent Considerations 

Washington appears increasingly prepared to move beyond traditional bilateral frameworks to counter China’s rapidly expanding nuclear arsenal while strengthening its deterrent against Russia and China. 

As DiNanno noted, future arms control agreements must address the “intolerable disadvantage” created by Russia’s large non-strategic (theater) nuclear arsenal — systems not covered by New START. They must also account for Moscow’s recently deployed and tested novel delivery systems, such as nuclear-powered cruise missiles, as well as China’s growing arsenal and advancing delivery capabilities. 

Absent effective arms control, DiNanno said the Trump administration may pursue a range of responses, including “expanding current forces, diversifying our capabilities, developing and fielding new theater range nuclear forces, and adapting our extended deterrence posture as necessary.” This approach appears prudent given the evolving strategic landscape marked by competition among three large nuclear powers. 

Jack Burnham is a senior research analyst in the China Program at the Foundation for Defense of Democracies (FDD). Andrea Stricker is a research fellow and deputy director of FDD’s Nonproliferation Program. Follow them on X @JackBurnham802 and @StrickerNonpro. For more analysis from Jack, Andrea, and FDD, please subscribe HERE. Follow FDD on X @FDD. FDD is a Washington, DC-based, nonpartisan research institute focusing on national security and foreign policy.