China's nuclear arsenal is likely to more than triple to 1,500 warheads by 2035, the Pentagon said in a Tuesday report that also highlighted the increasing sophistication of the country's air force.
Washington has identified Beijing as the most consequential challenge to the US, and the annual report on China's military emphasised improvements to both its nuclear and conventional forces.
"The Department of Defense estimates that (China's) operational nuclear warheads stockpile has surpassed 400," the report said. "If China continues the pace of its nuclear expansion, it will likely field a stockpile of about 1,500 warheads" by 2035.
That figure would still however lag far behind the arsenals of the US and Russia, which each include several thousand nuclear warheads.
China "probably intends to develop new nuclear warheads and delivery platforms that at least equal the effectiveness, reliability and/or survivability" of those under development by the US and Russia, the report said.
Pentagon spokesman Pat Ryder said Tuesday that an increased Chinese nuclear arsenal would be a source of instability.
"The more proliferation there is, the more concerning it is, the more destabilising to the region it is," Ryder told journalists.
The report also said Beijing is working to modernise its ballistic missile arsenal, launching some 135 in testing during 2021 – "more than the rest of the world combined," excluding those fired in conflicts.
China is "developing new intercontinental ballistic missiles (ICBMs) that will significantly improve its nuclear-capable missile forces," the report said.
And Beijing's air force – the third-largest in the world with more than 2,800 aircraft – is making strides.
It is "rapidly catching up to Western air forces and continues to modernise with the delivery of domestically built aircraft and a wide range of UAVs," according to the report.
"This trend is gradually eroding longstanding and significant US military technical advantages... in the air domain."
A senior US defense official, speaking before the report's release, said the Chinese air force is "trying to... progress rapidly on all fronts," including on the equipment it operates as well as its pilots and other personnel.
The report takes aim at the way in which China is employing its military in the Asia-Pacific region, saying it has "adopted more coercive and aggressive actions."
"Throughout 2021 and into 2022, (Chinese) vessels and aircraft have exhibited a sharp increase in unsafe and unprofessional behaviour," risking "a major incident or accident," the report said – an issue US Defense Secretary Lloyd Austin raised in a recent meeting with his Chinese counterpart Wei Fenghe.
China's military "increased provocative and destabilising actions" during 2021 around Taiwan, the self-governing democratic island Beijing claims as its own.
Beijing lashes out at any diplomatic action that might lend Taiwan legitimacy, and responded to an August 2022 visit by US House Speaker Nancy Pelosi by holding its largest and most aggressive exercises around the island since the 1990s.
Both sides have since moved to lower the temperature, but the senior defence official said that while Chinese military activity around Taiwan has decreased, it is still higher than before.
Beijing is "establishing kind of a new normal in terms of the level of military activity around Taiwan following the speaker's visit," the official said.
"Even though we don't see an imminent invasion, obviously, that sort of an elevated level of... intimidating and coercive activity around Taiwan" is a source of concern.