U.S. accuses China of secret nuclear tests as New START expires

U.S. Under Secretary of State Thomas DiNanno told the UN Conference on Disarmament on Feb. 6, 2026 that China conducted a secret nuclear test on June 22, 2020, using seismic decoupling to conceal the blast. China's Ambassador Shen Jian denied the charge and called the U.S. "the culprit for the aggravation of the arms race." The accusation came one day after New START expired, leaving no binding limits on U.S. or Russian warheads for the first time since 1972. China holds at least 600 warheads — up 20% in a single year — with the Pentagon projecting China will exceed 1,000 by 2030.