Investment in its nuclear arsenal is bringing China closer to equal status with Russia and the US and could yield it technical capabilities that neither of the two dominant nuclear powers currently possess.
U.S. intelligence agencies believe China is developing a new generation of nuclear weapons and has conducted at least one secret explosive test in recent years as part of a broader effort to completely transform its nuclear arsenal into the most technologically advanced in the world, according to multiple sources familiar with U.S. intelligence assessments.
The US assessment of China’s intention to radically advance its nuclear weapons is fueling debate within the intelligence community and beyond over whether there has been a shift in Beijing’s thinking on nuclear strategy, the sources say. Investment in its nuclear arsenal is bringing China closer to equal status with Russia and the US and could yield it technical capabilities that neither of the two dominant nuclear powers currently possess.
China secretly carried out an explosive nuclear test in June 2020 at the Lop Nur facility in the country’s northwest — despite a self-imposed moratorium on such activity in place since 1996 — and planned to do more in the future, according to the sources and recent statements from U.S. officials. Although the 2020 test was publicly released by U.S. State Department officials this month, the purpose of the test had not previously been revealed.
China also appears to be developing low-yield tactical nuclear weapons – something the country has never previously produced – that could be used against closer targets, including in scenarios where Beijing responds to a potential US defense operation on Taiwan, the sources added.
China has been aggressively expanding its nuclear facilities, according to previous public reports from US intelligence officials, with analysts suspecting that China may be developing new technologies. Now, US officials believe there is strong evidence to support this theory – in part – because of what they discovered about the 2020 test.
China has had a nuclear arsenal since 1964. It has produced warheads faster than any other country in the world, although the size of its arsenal is far behind that of Russia and the United States, which continue to hold most of the world’s nuclear weapons.
Asked about US intelligence assessments of its nuclear program, a spokesperson for China’s embassy in Washington told CNN that “the United States has distorted and defamed China’s nuclear policy.”
“This is political manipulation with the aim of seeking nuclear hegemony and evading its own responsibilities in terms of nuclear disarmament,” says Liu Pengyu. “China firmly opposes such narratives. US allegations about China carrying out a nuclear test are completely unfounded. China opposes any attempt by the United States to invent excuses to resume its own nuclear tests.”
A defense official said the Pentagon “does not comment on intelligence assessments related to specific alleged nuclear test events.”
The Pentagon said China’s efforts to expand and improve its nuclear arsenal could “provide [à China] new options before and during a crisis or conflict to use nuclear weapons for coercive purposes, including military provocations against U.S. allies and partners in the region.”
A 2024 Defense Information Agency report also noted that China is seeking to renew its nuclear arsenal with the US in mind.
“China is undergoing the most rapid expansion and most ambitious modernization of its nuclear forces in history – almost certainly driven by the objective of lasting strategic competition with the US and the goal of realizing intensified strategic concepts that have existed for decades but are now being realized,” the report states.
Historically, China has viewed its nuclear capabilities as a means of self-defense and a way to dissuade other countries from using or threatening to use their own nuclear weapons against it. China has maintained a policy of non-use in the first instance for decades, but the country’s proposal on global governance presented in 2023 makes no reference to this commitment, which has led to speculation that China’s stance could be changing.
And until recently, China’s nuclear capabilities were considered much less advanced than those of its nuclear rivals. The country has carried out far fewer tests from which it could gather data needed to design modernized weapons.
A member of the People’s Liberation Army looks on as the strategic strike group displays DF-61 nuclear missiles during a military parade to mark the 80th anniversary of the end of World War II, in Beijing, China, September 3, 2025. photo Tingshu Wang/Reuters/File
“China’s nuclear weapons experts may not trust the limited data they collected during just 45 tests, most of which were carried out in the atmosphere and with inadequate instruments,” says Jeffrey Lewis, an arms control expert at the Middlebury Institute of International Studies.
This is, in the opinion of American officials, one of the main reasons why China would be resuming explosives tests.
“They have a new generation of weapons for which they have no database,” said one of the sources familiar with the matter.
As part of this modernization push, China has invested heavily in maneuverability and survivability, multiple sources tell CNN, noting that Beijing has long feared that the US could potentially destroy its entire force before it can react — or at least inflict enough damage to effectively neutralize it.
American officials also believe that China has concerns about the reliability of its own systems, which contributes to the urgency surrounding its modernization efforts and fuels investment in technologies to ensure that its nuclear warheads can reach their intended target.
Two sources indicate that China appeared increasingly paranoid about a potential U.S. attack during the same period as the June 2020 nuclear test. In the run-up to the U.S. presidential election in November 2020, Chinese officials even contacted then-Chief of the Joint Chiefs of Staff Mark Milley because they were worried about an “October surprise,” the sources said.
Although these tensions eventually eased, China took steps in the following years to not only upgrade its nuclear forces but also modernize its entire military.
China’s nuclear ambitions have once again become a topic of intrigue in recent weeks after State Department officials revealed new details about what they allege was an explosive test carried out at the Lop Nur facility in June 2020 – releasing the exact date, location and seismic data related to the event to support its conclusion. The link with China also using the test to modernize its arsenal was clear in the subsequent study of the test, particularly given the seismic magnitude recorded, a former senior official tells CNN.
This week, Deputy Secretary of State Christopher Yeaw said at an event at the Hudson Institute think tank in Washington that the June 2020 event saw a 2.75 magnitude “explosion.”
“I have analyzed additional data since [e] there is very little possibility for me to say that it is anything other than an explosion, a singular explosion,” said Yeaw, adding that the data was not consistent with mining explosions.
“It’s also not at all consistent with an earthquake,” said the former intelligence analyst and defense official with a doctorate in nuclear engineering. “AND […] what you would expect from a nuclear test with explosives.”
Earlier this month, Under Secretary of State for Arms Control Thomas DiNanno also publicly accused China of secretly carrying out an explosive nuclear test in 2020 and suggested that the US had obtained information indicating that Beijing planned to carry out more tests.
“I can reveal that the US government is aware that China has conducted explosive nuclear tests, including preparation for tests with designated yields in the hundreds of tons; the PLA (People’s Liberation Army) sought to conceal the tests by obfuscating the nuclear explosions, as it recognized that these tests violate test ban commitments,” in a speech on February 6.
CNN has since learned that additional information gathered by the US after the June 2020 event served as a key piece of the puzzle, as experts argue that seismic data alone is not enough to definitively conclude that it was a nuclear test or understand why it was carried out.
When conducting secret nuclear tests earlier this month, Liu, the spokesman for the Chinese Embassy in Washington D.C., said China “follows a ‘no first use’ policy of nuclear weapons and a nuclear strategy that focuses on self-defense, and adheres to its moratorium on nuclear testing.”
“We stand ready to work with all parties to jointly defend the authority of the Comprehensive Nuclear-Test-Ban Treaty and safeguard the international nuclear disarmament and non-proliferation regime,” he said.
“The US is expected to sincerely fulfill its obligations under the Treaty and its commitment to a moratorium on nuclear testing and take concrete steps to defend the international nuclear disarmament and non-proliferation regime, as well as global strategic balance and stability,” he added to CNN.
The timing of the Trump administration’s decision to reveal details about an alleged test that took place nearly six years ago is also notable as it comes at a time when the US is insisting that China join any new nuclear weapons deal, a proposal that Chinese leader Xi Jinping has resisted until now, sources indicate.
Trump suggested the US could resume its own explosives testing.
Ultimately, China has more to gain from conducting explosive tests than the U.S., which raises questions about why the State Department made the rare decision to release details about the June 2020 event at this time, according to multiple sources.
That move suggests the Trump administration is concerned about public diplomacy with Beijing — especially ahead of the president’s upcoming trip to the country in April, noted a source familiar with discussions between the two countries.
But current U.S. officials also noted that the Trump administration is determined to involve China in a nuclear deal, suggesting that revealing some of what the U.S. knows about China’s current efforts could pressure the country into negotiations.
“The old arms control paradigm is collapsing as China races to increase its nuclear arsenal,” says Alex Gray, former NSC chief of staff and now senior fellow at the Atlantic Council. “The administration is dealing not only with Russian strategic weapons, but also with Chinese nuclear expansion, which is much more concerning. Unless we can negotiate an arms control framework that includes Beijing, the US does not need to blindly adhere to outdated arms control prescriptions that do not capture the threats of today and tomorrow.”
The PLA’s rapid growth and modernization also serves to fulfill Xi’s promise, made more than a decade ago, to transform the world’s largest armed forces into a world-class military force.
“This is a reflection of China’s global ambitions, […] It’s one of the clearest signs of almost everything China is doing,” says one of the sources, noting that Beijing’s actions should inform how the US prepares for future conflicts.
