US official alleges covert Chinese nuclear test in 2020

A senior United States official has alleged that China may have conducted a covert underground nuclear test in June 2020, citing seismic data recorded in Central Asia.

Speaking at the Hudson Institute in Washington on Tuesday, Assistant Secretary of State Christopher Yeaw said a remote seismic monitoring station in Kazakhstan detected what he described as a magnitude 2.75 “explosion” originating from the Lop Nor test site in western China on 22 June 2020.

According to Yeaw, the seismic signature was inconsistent with either mining activity or a natural earthquake. “It is what you would expect with a nuclear explosive test,” he said, adding that his assessment was based on additional data reviewed since the event.

The Lop Nor facility has historically been associated with China’s nuclear weapons testing programme. Beijing’s last acknowledged underground test took place in 1996.

However, the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), which operates a global monitoring system to detect nuclear explosions, said the available data were insufficient to substantiate the allegation. The organisation’s executive secretary, Robert Floyd, said its PS23 seismic station in Kazakhstan recorded two small seismic events 12 seconds apart on the date in question, but both were well below the detection threshold typically associated with nuclear tests of significant yield.

“With this data alone, it is not possible to assess the cause of these events with confidence,” Floyd said.

China firmly denied the accusation. Liu Pengyu, spokesperson for the Chinese embassy in Washington, described the claim as “entirely unfounded” and accused the United States of attempting to create a pretext for resuming its own nuclear testing.

He said Beijing remained committed to upholding the global norm against nuclear tests and called on Washington to honour its disarmament obligations.

The allegation comes amid heightened tensions over nuclear arms control. The New START treaty between the US and Russia expired on 5 February, fuelling concerns about a renewed strategic arms race. President Donald Trump has urged China to join Washington and Moscow in negotiating a new three-way framework to limit strategic nuclear arsenals, but Beijing has resisted the proposal, arguing that its stockpile is far smaller than those of the US and Russia.

The Pentagon estimates that China possesses more than 600 operational nuclear warheads and could exceed 1,000 by 2030 as it expands its strategic forces.

Both the US and China have signed but not ratified the 1996 Comprehensive Nuclear-Test-Ban Treaty. Under international law, signatories are expected to refrain from actions that would defeat the object and purpose of the agreement.

The United States last conducted an underground nuclear test in 1992 and has since relied on advanced simulation technologies to maintain its nuclear arsenal without live detonations.

With agency input