The United States accused China on Friday of carrying out a secret nuclear test in 2020, calling for a new arms control treaty that would include China alongside Russia. The allegations came during a global disarmament conference in Geneva, a day after the treaty limiting US and Russian missile and warhead deployments expired.
US Under Secretary of State for Arms Control and International Security Thomas DiNanno told the conference: “The US 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 China tried to conceal the tests using methods to reduce the effectiveness of seismic monitoring. DiNanno said one such test occurred on 22 June 2020.
President Donald Trump ordered the US military in October to resume its nuclear testing processes, citing other countries’ activities without specifying them.
China’s disarmament ambassador, Shen Jian, did not directly address the US allegations but said Beijing has always acted prudently on nuclear matters. “China notes that the US continues to hype the so-called China nuclear threat. China firmly opposes such false narratives,” he said.
International reactions and treaty context
Diplomats described the US accusations as new and concerning. China, like the US, has signed but not ratified the Comprehensive Nuclear Test Ban Treaty (CTBT), which prohibits explosive nuclear tests. Russia signed and ratified the treaty but withdrew its ratification in 2023.
Robert Floyd, head of the treaty’s Vienna-based governing body, said international monitoring did not detect any nuclear test explosions at the time of the alleged Chinese test. He added that further analyses have not changed this conclusion.
Daryl Kimball, director of the Arms Control Association, said the US should present any credible evidence to the treaty’s governing body and pursue technical discussions with China and Russia. He warned that resuming US testing would risk prompting a chain reaction of nuclear tests by other powers.
Future arms control and security concerns
The 2010 New START treaty, which expired on Thursday, left the US and Russia without binding limits on strategic missile and warhead deployments. The US has proposed a new agreement including China, citing Beijing’s growing arsenal. US Secretary of State Marco Rubio stated that China and Russia should not expect the US to remain passive while expanding their nuclear forces.
DiNanno said a bilateral treaty with only one nuclear power is “simply inappropriate in 2026 and going forward.” He also projected that China could have more than 1,000 nuclear warheads by 2030. Shen reiterated that China would not join new negotiations at this stage, noting the country has fewer warheads than the US or Russia.
Experts said negotiating a new nuclear arms control agreement could take years, while current geopolitical tensions increase the risk of miscalculation. Russia said it is ready for any scenario, with Foreign Minister Sergei Lavrov noting that talks with the US had reached an understanding of responsible behaviour. NATO allies Britain and France emphasised that the largest nuclear powers should reach an understanding to prevent further weakening of nuclear norms.
