New START ends: US accuses China of secret nuke tests, warns Beijing's 'arsenal has no limits, no transparency'

US pressures China on nuclear talks

The United States on Friday accused China of secretly conducting nuclear explosive tests, while Washington and Moscow stressed the urgent need to begin fresh arms control talks following the expiration of the last remaining US–Russia nuclear treaty.

The allegation comes amid renewed US pressure on Beijing to participate in any future nuclear arms agreements.

US Secretary of State Marco Rubio warned that an arms control framework excluding China would leave the United States and its allies “less safe,” citing China’s rapidly expanding nuclear arsenal.

Speaking at the UN-backed Conference on Disarmament in Geneva, top US arms control official Thomas DiNanno alleged that China had carried out covert nuclear tests and attempted to conceal them.

“The US government is aware that China has conducted nuclear explosive tests, including preparing for tests with designated yields in the hundreds of tons,” DiNanno said, according to the Associated Press (AP).

He added that China’s military sought to hide the activity because it knew such tests violated international commitments to suspend nuclear testing.

China strongly rejected the claims. Ambassador Shen Jian called the allegations “false narratives and unfounded accusations,” insisting that Beijing continues to honour its pledge to suspend nuclear testing.

US criticism “is aimed at shifting responsibility for nuclear disarmament and justifying American ‘nuclear hegemony,’” Shen told AP.

New START expires, US and Russia discuss next steps

The sharp exchange came a day after the New Strategic Arms Reduction Treaty (New START) formally expired, removing limits on the world’s two largest nuclear arsenals for the first time in more than 50 years. The treaty had capped each side at 1,550 deployed nuclear warheads.

Russian and US negotiators met in Abu Dhabi to discuss the future of nuclear arms control. According to Kremlin spokesman Dmitry Peskov, both sides “understood the importance of acting responsibly and beginning negotiations as soon as possible,” reported AP.

Russian President Vladimir Putin offered to maintain New START limits for another year if Washington agreed, but US President Donald Trump has rejected the proposal, instead calling for a “new and broader agreement” that includes China.

Asked about a possible informal extension of the treaty limits, Peskov said any extension would need to be formal. The US and Russia have also agreed to restore high-level military-to-military dialogue, suspended since 2021.

China refuses to join talks

Washington says China’s expanding nuclear stockpile makes its inclusion essential. Rubio wrote that China’s arsenal had grown from the low 200s to more than 600 warheads since 2020 and could exceed 1,000 by 2030.

“As we sit here today, China’s entire nuclear arsenal has no limits, no transparency, no declarations and no controls,” DiNanno said.

China, however, has refused to take part in disarmament talks at this stage. Ambassador Shen argued that Beijing’s nuclear capabilities are not comparable to those of the US or Russia and urged the two largest nuclear powers to take primary responsibility for disarmament.

He also expressed regret over New START’s expiry and called on Washington to accept Moscow’s offer to temporarily maintain its limits.

Renewed arms race concerns

Together, Russia and the US control over 80 per cent of the world’s nuclear warheads, while China’s arsenal is expanding faster than any other country’s.

The lapse of New START has raised fears of a renewed nuclear arms race, as no binding framework now exists to restrain the most destructive weapons.

Despite widespread agreement on the need for negotiations, major differences remain over the structure of any future deal: Washington pushes for a three-way agreement, Moscow suggests including other nuclear powers, and Beijing continues to refuse participation.