The timing of the alleged test, revealed by Washington at a global disarmament forum, is likely to sharpen strategic concerns in New Delhi over China’s military posture during one of the most volatile phases of the India-China border crisis in decades.
US accusation; China’s response
“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,” U.S. Under Secretary of State for Arms Control and International Security Thomas DiNanno told the Disarmament Conference in Geneva.
He added that the Chinese military “sought to conceal testing by obfuscating the nuclear explosions because it recognized these tests violate test ban commitments. China has used ‘decoupling’, a method to decrease the effectiveness of seismic monitoring, to hide their activities from the world.”
DiNanno said Beijing conducted one such “yield-producing test” on June 22, 2020.
China did not directly address the specific allegation.
Its ambassador on disarmament, Shen Jian, said Beijing had “always acted prudently and responsibly on nuclear issues” and accused Washington of exaggerating threats.
“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,” Shen said, adding, “It (the US) is the culprit for the aggravation of the arms race.”
Arms control flashpoint
The accusation surfaced at a critical juncture for global nuclear stability–a day after the expiry of the 2010 New START treaty, which had capped U.S. and Russian strategic missile and warhead deployments.
With the treaty lapsing, Washington and Moscow are now without binding nuclear limits for the first time in more than half a century, raising fears of renewed arms competition.
DiNanno argued that the changing threat environment makes older bilateral arrangements inadequate.
“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,” he said.
The U.S. projects that China’s nuclear arsenal could exceed 1,000 warheads by 2030, though Beijing maintains it possesses far fewer—around 600 compared with roughly 4,000 each for the United States and Russia—and has rejected joining trilateral negotiations for now.
Strategic vacuum
Security analysts known to Reuters warn that the absence of New START creates a dangerous strategic void reminiscent of early Cold War uncertainty, when fears of miscalculation between nuclear powers were at their peak.
If no replacement treaty emerges, major powers could feel compelled to expand arsenals based on worst-case assumptions, particularly as China rapidly modernises its nuclear capabilities.
Russia has signalled readiness for dialogue with Washington on future arms control, while also preparing for any scenario. Britain and France have supported calls for a new multilateral framework that includes China, citing concerns over Beijing’s expanding arsenal and the broader weakening of nuclear norms.
The Galwan clash marked the first combat fatalities on the India-China border in 45 years, triggering prolonged military standoffs, rapid force mobilisation, and an enduring deterioration in bilateral ties.
