China has expanded and upgraded several nuclear-related sites hidden in the valleys of Sichuan Province in recent years, The New York Times reported on Saturday, citing satellite imagery.
Experts have said that developments shown in the images align with Beijing’s broader push to modernize and expand its nuclear arsenal.
The activity, centered on secret research locations including Zitong and Pingtong, came as global arms-control frameworks face a new strain following the recent expiration of the New START treaty between the United States and Russia.
The sites, first built decades ago under Mao Zedong’s “Third Front” effort to shelter sensitive weapons work from attack, appear to be receiving sustained new investment since about 2019, analysts said.
One of the most prominent locations, Pingtong, features a refurbished main structure and a 360-foot-high ventilation stack, while nearby construction continues, the analysis found.
What is at secretive Chinese nuclear-related research facilities?
At Zitong, engineers have reportedly built new bunkers and ramparts and added a complex dense with piping, a layout that specialists say can indicate handling of hazardous materials.
Analysts and outside experts cited by the NYT said the site may be linked to high-explosive testing used to refine the implosion systems that can trigger a nuclear chain reaction.
At Pingtong, the double-fenced compound’s design has led some experts to assess that it could be connected to producing plutonium “pits,” the metal cores of many nuclear warheads.
Large characters above the entrance reportedly display a slogan associated with President Xi Jinping, “Stay true to the founding cause and always remember our mission,” visible in satellite imagery, underscoring the political sensitivity of the work.
China’s nuclear buildup is already a growing point of friction with Washington, which has argued that any future arms-control arrangement should include Beijing.
The Pentagon has estimated China had more than 600 nuclear warheads by the end of 2024 and is on track to reach 1,000 by 2030, figures that have fueled debate over how the larger force could shape crisis behavior, including scenarios involving Taiwan.
China, whose stockpile remains smaller than those of the United States and Russia, has repeatedly shown little interest in joining such frameworks, US officials and arms-control analysts say.
Collapse of US-Russia START treaty
The timing of the reported upgrades is also significant because New START, the last remaining treaty limiting US and Russian strategic nuclear forces, has now expired, leaving a vacuum in formal nuclear arms limits.
Because of this, Washington has renewed calls for broader talks that would also cover China, while Beijing has continued to resist being bound by US-Russia frameworks.
US allegations in recent weeks that China conducted secret nuclear explosive tests, which Beijing has denied, have further complicated already tense diplomacy.
Experts have publicly debated the strength of the evidence behind those accusations, highlighting how verification disputes can escalate mistrust.