A senior United States arms control official has revealed newly declassified information about what Washington believes was an underground nuclear test conducted by China nearly six years ago, while urging the international community to press both Beijing and Moscow toward greater transparency and renewed commitments to nuclear disarmament. The disclosure comes at a sensitive moment following the expiration of the last remaining nuclear arms control agreement between the United States and Russia, raising fears of a renewed global arms race.
Christopher Yeaw, the US Assistant Secretary of State for Arms Control and Non-Proliferation, presented the details before the UN-backed Conference on Disarmament, arguing that existing arms control frameworks failed to address China’s rapidly expanding nuclear capabilities. He warned that Beijing’s nuclear arsenal has grown quickly and largely without international oversight, adding that the United States believes China could reach nuclear parity with other major powers within four to five years if current trends continue.
According to Yeaw, monitoring systems detected a seismic event measuring magnitude 2.75 at China’s Lop Nur nuclear test site in western China on June 22, 2020. Based on comparisons with historical data, US analysts assessed the event as a probable underground explosion rather than a natural earthquake or routine mining activity. He also criticised China for limiting international monitoring efforts, noting that Beijing has rejected proposals to allow seismic monitoring stations at distances comparable to those permitted near US testing facilities in Nevada.
China strongly rejected the allegations, describing them as baseless accusations intended to justify renewed US nuclear testing. Beijing’s ambassador to the conference accused Washington of distorting China’s nuclear policy and attempting to evade its own arms control obligations. Chinese officials maintained that the country continues to support the objectives of the Comprehensive Nuclear-Test-Ban Treaty and has adhered to commitments to suspend nuclear testing.
The dispute unfolds against a broader backdrop of deteriorating arms control architecture. With the expiration of the New START treaty removing limits on US and Russian nuclear arsenals, concerns have grown about an unchecked expansion of global nuclear stockpiles. Yeaw argued that one of the treaty’s key shortcomings was its failure to include China, whose arsenal has expanded from roughly a few hundred warheads in 2020 to more than 600 today, with projections suggesting it could exceed 1,000 by 2030.
China, however, insists that its nuclear forces remain significantly smaller than those of the United States and Russia and argues that it is unreasonable to expect participation in trilateral arms control negotiations under current strategic conditions. Chinese representatives said their country faces a different security environment and therefore cannot be subject to the same obligations imposed on larger nuclear powers.
The United States has indicated it is pursuing multiple diplomatic pathways to address growing nuclear risks, including bilateral discussions, smaller multilateral arrangements and broader international negotiations. Washington has also urged other nations to encourage China and Russia to engage more actively in arms control efforts, warning that continued expansion of nuclear arsenals without transparency could destabilise global security and accelerate a new era of nuclear competition.
