Trump's Arms Control Chief Accuses China of Secret Nuclear Testing

The collapse of the New START framework has exposed a widening strategic vacuum, now sharpened by U.S. allegations that China conducted a covert nuclear explosive test in 2020.

Speaking at a Disarmament Conference in Geneva on Friday, U.S. Under Secretary of State for Arms Control and International Security Thomas DiNanno said Washington was pressing for a broader arms control treaty that would include China alongside Russia, a day after the 2010 New START accord expired, ending limits on U.S. and Russian strategic missiles and warheads for the first time since 1972.

Hidden Tests, Public Accusations

DiNanno told delegates: “I can reveal that the U.S. government is aware that China has conducted nuclear explosive tests, including preparing for tests with designated yields in the hundreds of tons.” He added that Beijing had used “decoupling”, a technique intended to reduce the effectiveness of seismic monitoring, and said China carried out one such “yield-producing test” on June 22, 2020.

According to DiNanno, the Chinese military sought to obscure evidence because it recognized such activity violated test ban commitments.

China’s ambassador on disarmament, Shen Jian, rejected the framing. “China notes that the U.S. continues in its statement to hype up the so-called China nuclear threat. China firmly opposes such false narratives,” he said, adding that Washington “is the culprit for the aggravation of the arms race.”

Diplomats at the Geneva meeting described the U.S. claims as new and concerning.

A Post-New START Strategic Gap

New START, signed in 2010, constrained U.S. and Russian deployments for more than a decade. Its expiry leaves both countries without binding caps on strategic arsenals.

DiNanno argued that bilateral limits no longer fit today’s multipolar landscape.

Today, the United States faces threats from multiple nuclear powers. In short, a bilateral treaty with only one nuclear power is simply inappropriate in 2026 and going forward.

U.S. Arms Control Chief Thomas DiNanno

Washington reiterated projections that China will exceed 1,000 nuclear warheads by 2030, a trajectory President Donald Trump has said could bring Beijing to parity with the United States and Russia within four to five years.

Beijing counters that its stockpile remains far smaller, estimated at about 600 warheads compared with roughly 4,000 each for the United States and Russia. Shen said China would not join negotiations at this stage and urged Washington to abandon Cold War thinking in favor of cooperative security.

“They Test Underground”

The new allegations by the arms chief echo earlier remarks by U.S. President Donald Trump. On Nov 3, he said that Pakistan, North Korea, China and Russia were testing. “They test underground where people don’t know exactly what is happening”, he said.

The current push for a wider treaty also comes as Washington highlights emerging technologies. Russia is developing “exotic” systems including the Burevestnik cruise missile and the Poseidon underwater torpedo, while Trump has pledged to build a space-based “Golden Dome” missile defense shield.

Arms Control Meets the Space Race

Critics note parallel U.S. initiatives that complicate Washington’s message on restraint. In August 2025, documents seen by Politico showed new NASA head Sean Duffy, also serving as Transportation Secretary, seeking to fast-track construction of a nuclear reactor on the Moon as part of Trump’s drive to win a “second space race” against China. The juxtaposition underscores how strategic competition now spans nuclear forces, missile defense, and space-based infrastructure.

With New START gone, analysts warn that reliance on worst-case assumptions could drive higher deployments and sharper rivalry, particularly as China accelerates its buildup.

The negotiating environment has shifted markedly since 2010, and any successor agreement would have to contend with new weapons systems, expanding arsenals, and deepening mistrust across three major nuclear powers.