Why China’s nuclear arsenal is under fire as US-Russia pact falls apart

The United States has accused China of conducting a secret nuclear test in 2020, alleging a violation of a 1996 test ban treaty understanding. The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), the international body that monitors nuclear explosions, refuted the US claim, stating its monitoring system detected no event consistent with a nuclear weapon test at the time. This accusation coincides with the US declining to extend its New Start treaty with Russia and urging China to join a new arms control agreement. China has rejected this proposal, citing the smaller size of its nuclear arsenal compared to those of the US and Russia. The timing of the US accusation highlights growing tensions surrounding global arms control and anxieties about China's expanding nuclear capabilities.

In February 2026, US Under Secretary of State Thomas DiNanno accused China at a UN disarmament conference in Geneva of conducting clandestine nuclear tests in 2020, violating nuclear test ban treaties. DiNanno claimed China concealed these tests, including one on June 22, 2020, to obfuscate the explosions. These accusations came shortly after the expiration of the New START treaty between the US and Russia, with DiNanno advocating for new nuclear weapons control agreements. However, the Comprehensive Nuclear-Test-Ban Treaty Organization stated that its monitoring system detected no event consistent with a nuclear weapon test explosion at the time of the alleged Chinese test, and that assessment remains unchanged. The US wants China to join a new nuclear weapons treaty after the expiration of the New START accord.

In July 2024, the United States accused China of conducting a secret nuclear test in 2020, specifically on June 22nd. The accusation was made by US Under Secretary of State Thomas DiNanno at a Disarmament Conference in Geneva. DiNanno stated that China concealed the testing by obfuscating the nuclear explosions and using decoupling methods to decrease the effectiveness of seismic monitoring. The US claims the test involved a yield-producing explosion in the hundreds of tonnes. The US is calling for a broader arms control treaty that includes China and Russia. The accusation highlights tensions between the US and China regarding nuclear arms control.