(CNN) China is rapidly expanding its nuclear arsenal and may have 1,000 nuclear warheads by the end of the decade as it aims to surpass US global influence by the middle of the 21st century, according to a major Pentagon report released on Wednesday.
The estimate, based on the rapid modernization of China's nuclear strike options and its construction of missile silos, marks a dramatic increase from the projection in last year's China Military Power report, which estimated that China would double their stockpile of 200 warheads within a decade.
The report comes amid heightened tensions over the issue of Taiwan and was published hours after the most senior US general, Chairman of the Joint Chiefs of Staff Mark Milley issued a stark warning about China's military progress stating it amounts to "one of the largest shifts in global geostrategic power that the world has witnessed."
A senior defense official briefing reporters on the report adopted a similar stance.
"The nuclear expansion that the [People's Republic of China] is undertaking is certainly very concerning to us," the official said. "It's one thing to observe what they're doing, but they haven't really explained why they're doing it."
The official said the buildup raises serious doubts about the intent behind their nuclear stockpile.
"They're moving in a direction that substantially exceeds where they've been before in terms of numbers and capabilities," the official said. Though China still maintains a no first-use policy when it comes to nuclear weapons, the official said China has suggested "there are circumstances under which that wouldn't apply."
China has also focused on a "lean and effective nuclear force," but their current buildup is greater than the US anticipated "and well beyond where they've been historically." The investment in its nuclear force has allowed China to establish a "nascent" nuclear triad of air-launched ballistic missiles, as well as surface and sea-launched missiles, similar to the United States' own triad.
The US currently has 3,750 nuclear warheads in its stockpile, according to the latest data from the State Department, dwarfing the size of China's nuclear stockpile.
The Federation of American Scientists (FAS) published a report this week about the rapid building of three suspected silo fields in western China. The silo fields are still years away from becoming operational, wrote the authors of the FAS report, Matt Korda and Hans M. Kristensen, but they could eventually be capable of launching long-range nuclear missiles.
The Pentagon report, officially called Military and Security Developments Involving the People's Republic of China 2021, also focuses on Beijing's goals for future development and modernization of its armed forces. Crucially, if China meets its interim modernization goal for 2027, it could provide Beijing with "a range of different options" regarding Taiwan, from a blockade of the island to a potential amphibious invasion of either Taiwan itself or one of the smaller outlying islands.
At the same time, China also aims to deter foreign intervention in what Beijing sees as a domestic political issue.
"Obviously, they're looking at the United States or other parties they think might intervene on Taiwan's behalf," the official said. Beyond 2027, China is looking to complete modernization of its military by 2035 and become a world class military by 2049, the 100th anniversary of the establishment of the People's Republic of China (PRC). That would allow it to "displace US alliances and security partnerships in the Indo-Pacific region," the report said.
The report, which summarizes Chinese military developments during 2020, does not describe China's recent hypersonic missile test over the summer. On Wednesday at the Aspen Security Forum, where he was interviewed by NBC's Lester Holt, Milley said hypersonic technology is just one area where China is making significant advances.
Asked about the recent test of a hypersonic weapon, Milley said it was just one part of the broader picture with regard to China's rapidly advancing military capability, which he characterized as a "fundamental change" in warfare that is already reshaping elements of international order.
The report does note that China fielded the DF-17 last year, a medium-range ballistic missile capable of launching a hypersonic glide vehicle.
China has denied it has tested hypersonic weapons.
Last week, the second most senior US general said that the pace at which China's military is developing capabilities is "stunning" while US development suffers from "brutal" bureaucracy. The outgoing Vice Chairman of the Joint Chiefs of Staff, General John Hyten, told reporters at a Defense Writers Group roundtable that "the pace they're moving and the trajectory they're on will surpass Russia and the United States if we don't do something to change it. It will happen. So I think we have to do something."
The Pentagon has repeatedly referred to China as the "pacing challenge" for the US, but President Joe Biden stressed Tuesday that competition does not make conflict inevitable.
At the closing press conference of the COP26 climate summit, Biden said, "There's no reason there need to be conflict." Of his upcoming virtual summit with Chinese President Xi Jinping, Biden said, "I've also indicated to him, so I'm not reluctant to say it publicly, that we expect him to play by the rules of the road."
This year's report adds a new section on China's chemical and biological research, raising concerns about the possible dual-use applications of the country's biological activities. But it does not dive into the origins or spread of coronavirus. Instead, it notes that the Covid-19 pandemic was a driving force behind the China's foreign policy, as it sought to deflect any blame for the outbreak while using foreign assistance to build regional influence.