The US government wants Beijing to join a new nuclear weapons treaty after the New START agreement between the US and Russia expires.
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Published February 7, 2026
International observers said they saw no evidence to support claims by senior US officials who accused China of conducting a series of secret nuclear tests in 2020 and covering up activities that violate the Nuclear-Test Ban Treaty.
U.S. Under Secretary of State for Arms Control and International Security Thomas DiNanno made this assertion about China at the United Nations Conference on Disarmament in Geneva, Switzerland, on Friday, just days after the nuclear treaty with Russia expired.
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“I can make clear that the U.S. government is aware that China has conducted a nuclear test, including preparations for a test with a designated yield of several hundred tons,” DiNanno said at the conference.
The Chinese military “recognized that the nuclear test was a violation of the promise of a no-test, so it tried to cover up the test by obscuring the nuclear explosion,” he said.
“China conducted one nuclear test that produced such a yield on June 22, 2020,” he said.
DiNanno also made his case in a series of posts on social media, calling for a “new structure” in nuclear weapons control agreements after the New START treaty with Russia expired this week.
“New START was signed in 2010, and by 2026, restrictions on warheads and launchers will no longer be relevant as some nuclear-weapon states expand their armaments at a scale and pace unparalleled in more than half a century, and others continue to maintain and develop a wide range of nuclear systems unconstrained by the terms of New START,” he said.
Robert Floyd, executive director of the Comprehensive Nuclear-Test Ban Treaty Organization, said in a statement Friday that the organization’s monitoring systems “did not detect any events consistent with the detonation characteristics of a nuclear weapons test” during China’s alleged nuclear test, adding that that assessment remained unchanged after further detailed analysis.
China’s ambassador for nuclear disarmament, Shen Jian, did not directly address Mr. DiNanno’s accusations at the meeting, but said that while the United States “continues to distort and denigrate China’s national defense capabilities in its statements,” China has always acted prudently and responsibly on nuclear issues.
“We firmly oppose this false report and reject the baseless accusations made by the United States,” Shen said.
“In fact, the series of negative actions by the United States in the field of nuclear arms control is the greatest source of risk to international security,” he said.
“China has always respected its commitment to suspend nuclear testing,” Shen later said on social media.
Diplomats attending the meeting said the U.S. allegations were new and worrying.
Like the United States, China is a signatory to the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which bans explosive nuclear tests, but has not ratified it. Russia signed and ratified it, but withdrew its ratification in 2023.
US President Donald Trump previously told the US military to prepare to resume nuclear tests and said other countries were also conducting nuclear tests without providing details.
The US president said on October 31 that the US government would begin testing nuclear weapons “on the same basis” as the governments of Moscow and China, but did not provide details or explanation of what types of nuclear tests he wanted to resume.
He has also said he wants China to be involved in a future nuclear treaty, but authorities in Beijing have shown little interest in his proposals.
