BY COMFORT OGBONNA
The United States on Friday accused China of carrying out a covert nuclear test in 2020, dramatically escalating tensions between Washington and Beijing at a critical moment for global arms control.
The allegation was made at an international disarmament conference just one day after the expiration of the treaty that for years limited U.S. and Russian deployments of strategic missiles and nuclear warheads, leaving the world’s two largest nuclear powers without binding constraints for the first time in decades.
Speaking at the conference in Geneva, U.S. Under Secretary of State for Arms Control and International Security Thomas DiNanno said Washington was aware that China had conducted nuclear explosive tests, including preparations for tests with yields in the hundreds of tons.
He alleged that Beijing had deliberately sought to conceal these activities, arguing that Chinese military authorities obscured nuclear explosions because they knew such actions violated commitments related to nuclear test bans.
According to DiNanno, China employed a technique known as “decoupling” to reduce the effectiveness of seismic monitoring systems and hide the tests from international detection. He said one such yield-producing test took place on June 22, 2020.
China’s ambassador for disarmament, Shen Jian, did not directly address the specific accusation but firmly rejected Washington’s broader claims. He said China had consistently acted prudently and responsibly on nuclear matters and accused the United States of exaggerating what he described as a so-called Chinese nuclear threat. Shen argued that Washington, not Beijing, was responsible for aggravating the global arms race, and urged the U.S. to abandon what he called Cold War thinking in favor of cooperative and shared security approaches.
Diplomats attending the conference said the U.S. allegations were new and deeply concerning, underscoring the fragile state of global arms control just as the New START treaty formally expired. The 2010 agreement had for years capped the number of deployed strategic nuclear warheads and delivery systems held by the United States and Russia. Its expiration leaves the two rivals without any formal limits on their nuclear forces for the first time since the early 1970s, creating what analysts describe as a dangerous vacuum.
U.S. President Donald Trump has said he wants to replace New START with a broader agreement that would include China, arguing that the nuclear balance has changed significantly since the treaty was signed. At the Geneva conference, DiNanno said the United States now faces threats from multiple nuclear powers and that a bilateral treaty involving only one counterpart was no longer appropriate going forward. He reiterated U.S. projections that China’s nuclear arsenal could exceed 1,000 warheads by 2030.
China, however, has repeatedly resisted calls to join trilateral negotiations with Washington and Moscow. Shen restated Beijing’s position that it would not take part in new talks at this stage, noting that China’s arsenal remains far smaller than those of the United States and Russia. While Beijing is estimated to have around 600 nuclear warheads, both Washington and Moscow are believed to each possess roughly 4,000. Shen said meaningful arms control should begin with countries holding the largest arsenals and emphasized the need for mutual trust and restraint.
The expiry of New START marks the first time since 1972 that there are no binding agreements governing U.S. and Russian strategic nuclear forces. During the Cold War, arms control treaties were seen as essential tools to reduce the risk of catastrophic miscalculation and to prevent an economically and strategically destabilizing arms race. Analysts warn that without a replacement agreement, both sides may be forced to rely on worst-case assumptions about the other’s intentions, increasing incentives to expand their arsenals, particularly as China continues to modernize its forces.
Russia has said it prefers to maintain dialogue with the United States on nuclear arms control, but has also signaled readiness for any outcome. Foreign Minister Sergei Lavrov said Moscow was prepared for all scenarios, while the Kremlin indicated that recent talks between Russian and U.S. officials included an understanding that both sides would act responsibly. Russia has also argued that the nuclear forces of Britain and France should be included in future negotiations, a position those countries have rejected.
At the Geneva forum, Britain said the moment called for a new era of arms control that would bring China, Russia and the United States to the table, adding that it shared U.S. concerns about the rapid expansion of China’s nuclear capabilities. France echoed the need for an agreement among states with the largest arsenals, warning that global nuclear norms are weakening at an unprecedented pace.
Experts caution that negotiating any new arms control deal will be extremely complex and time-consuming, especially given how much the strategic landscape has shifted since 2010. Russia is developing new weapons systems, including the Burevestnik nuclear-powered cruise missile and the Poseidon underwater nuclear torpedo, while Trump has pledged to pursue a space-based “Golden Dome” missile defense system. Analysts say years could pass before a new treaty is reached, leaving a prolonged period of uncertainty amid heightened geopolitical tensions over Ukraine, the Middle East and other global flashpoints.
Some security specialists warn that the breakdown of arms control and the failure of major powers to agree on new limits could have far-reaching consequences. Prolonged uncertainty, they say, may intensify debates in countries such as Japan, South Korea and Poland about whether they should pursue their own nuclear capabilities, potentially reshaping the global security order in ways that would be difficult to reverse.