GENEVA — The United States accused China on Friday of conducting secret nuclear tests, reviving concerns about global arms control at a time when existing treaties are unraveling. According to U.S. officials, Beijing carried out at least one covert nuclear test in 2020, raising alarms about transparency and compliance with international norms.

The accusation comes as Washington pushes for a new, broader arms control treaty that would include China alongside Russia. With the expiration of the New START treaty between the U.S. and Russia, there is currently no binding agreement limiting the deployment of nuclear weapons for the first time since 2010. Analysts warn this creates a more dangerous environment with a higher risk of miscalculation.

China has not directly responded to the U.S. claim but has insisted it acts responsibly on nuclear issues. Beijing has long maintained that its nuclear arsenal is modest compared to those of Washington and Moscow, and that it adheres to a “no first use” policy.

The U.S. revelation is part of a broader strategy to pressure China into joining future arms control negotiations. “We cannot ignore the fact that China is modernizing and expanding its nuclear forces,” one senior U.S. official said, stressing that any future treaty must account for Beijing’s capabilities.