The Trump administration has accused China of secretly testing a nuclear weapon in 2020. The group that monitors nuclear tests worldwide, the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), says it couldn’t confirm a test actually occurred. China has rejected the accusations, calling them a distortion of its nuclear policy.
Instead of treating this as a technical disagreement for international institutions to sort out, the Trump administration appears to be using these claims to push for restarting U.S. nuclear testing “on an equal basis.” Last October, President Trump announced he had instructed the Pentagon to "begin testing our nuclear weapons.”
This is a dangerous path. The U.S. has held off on nuclear testing since 1992. Russia (then the Soviet Union) declared its moratorium in 1991. China followed in 1996, signing the Comprehensive Test Ban Treaty (CTBT) shortly thereafter. Breaking this longstanding norm based on unsubstantiated claims could spark a new wave of nuclear detonations without resolving anything.
If U.S. officials truly believe China broke the testing moratorium, the appropriate response is simple: present verifiable evidence to the CTBT community, and push for stronger verification measures. Tossing out accusations without verifiable proof is how states drift into escalation.
What US officials are alleging
Earlier this month, Undersecretary of State Thomas DiNanno said that the U.S. believes China carried out “yield-producing” nuclear explosive tests, including one on June 22, 2020, at the Lop Nur test site in northwestern China.
Last week, Assistant Secretary Christopher Yeaw gave more details. He pointed to a seismic signal at 09:18 UTC, arguing it looked more like an explosion than an earthquake or mining activity. U.S. officials also accused China of using “decoupling,” which is a technique to try to hide the seismic signature of a test.
The administration has also made similar accusations against Russia, but the charges against China are more specific, naming a date, place, and method.
The timing here matters. These allegations emerged the same week New START expired, leaving the U.S. and Russia with no binding limits on strategic weapons for the first time in decades. Secretary of State Marco Rubio has argued that bilateral U.S.-Russia frameworks are now “obsolete” and that China must be included in any future agreement, despite the fact that China’s arsenal is much smaller than Russian and American stockpiles. Pointing the finger at China for secretly testing conveniently supports that narrative and gives the U.S. cover to walk away from its own restraint.
U.S. intelligence reportedly has assessed that this alleged test is part of a broader Chinese campaign to develop a new generation of nuclear weapons, including low-yield tactical nuclear weapons.
What the experts say
The administration’s charge clashes with what the world’s central technical authority for detecting nuclear explosive tests says.
CTBTO Executive Secretary Robert Floyd explained that for the date in question, the organization’s monitoring system “did not detect any event consistent with the characteristics of a nuclear weapon test explosion at that time,” and that subsequent detailed analysis had not changed that conclusion.
CTBTO sensors picked up two small seismic events 12 seconds apart at the specified time and date, but they were way too weak to count as likely nuclear explosions (the system’s threshold is about 500 tons of TNT). With the available data, the CTBTO said it can’t confidently say what caused the events.
Floyd pointed to what is missing: the CTBT's strongest verification tools, including short-notice on-site inspections, can only be activated once the treaty enters into force. The U.S. has signed the CTBT but never ratified it. Neither has China. Russia signed and ratified it but later withdrew.
Norway’s NORSAR, an independent seismic monitoring institution, also checked the data and reached a similar conclusion. It found a small event at the same time, but said it “cannot confirm or refute a nuclear test” from the available seismic data, and that the event could have been a small natural earthquake.
In short, we’re on the verge of restarting nuclear testing, even though the public technical record can’t settle the question, and the verification tools aren’t available because the treaty that created them isn’t in force.
What the US should do instead
If Washington really has a strong case that China tested a nuclear weapon, it should rally international support to hold Beijing accountable. If the evidence isn’t solid enough to share, it’s not solid enough to break decades of nuclear testing restraint.
There are clear steps forward. The U.S., China, and Russia should ratify the CTBT so that the world can actually use the verification tools designed for situations just like this.
With the Non-Proliferation Treaty Review Conference coming up in April, Washington could push for a political declaration by the five major nuclear-armed states (the U.S., Russia, China, France, and the UK), reaffirming the testing moratorium. U.S. officials are already meeting with delegations from these countries for nuclear arms control talks. Reaffirming the test ban would give the U.S. the moral authority to demand openness from others.
The Trump-Xi summit in early April presents another opportunity. If the U.S. wants China at the arms control table, it should arrive in Beijing with concrete proposals for verification, not just finger-pointing that kills trust before talks even begin. These are narrow windows for the U.S. to lead on verification and risk reduction.- Nuke treaty loss a 'colossal' failure that could lead to nuclear arms race ›
- Reckless posturing: Trump says he wants to resume nuke testing ›
