WASHINGTON -- China is developing hypersonic weapons at a "stunning" pace, conducting "hundreds" of tests to Washington's nine over the past five years, a top Pentagon official told reporters.

Beijing has been willing to move fast and learn from its failures, while the Department of Defense has been held back by "brutal" bureaucracy, Gen. John Hyten, the outgoing vice chairman of the Joint Chiefs of Staff, America's No. 2 uniformed military officer, said Thursday.

Beyond the direct threat they could pose to the U.S., hypersonic weapons could affect the balance of military might in the Pacific at a time when tensions are simmering in the region, particularly over Taiwan.

Hyten's comments came the day after Gen. Mark Milley, chairman of the Joint Chiefs of Staff, called China's testing "very close to" a "Sputnik moment," referring to the old Soviet Union's 1957 launch of the world's first artificial satellite, which sparked its space race with the U.S.

The biggest fear for President Joe Biden's administration is China gaining the capability to reliably strike targets in the continental U.S. This past summer, China tested a nuclear-capable missile with a hypersonic glide vehicle that circled Earth in orbit before striking its target -- a weapon that could theoretically reach anywhere in the world.

This vastly increased range opens up the possibility of an attack on the U.S. from the south flying on a path over Antarctica, which would pose a problem for American missile defense systems largely built on the expectation of strikes coming from the north.

Gen. Mark Milley, chairman of the Joint Chiefs of Staff, has said China's hypersonic missile tests come "very close" to a "Sputnik moment."   © Reuters

The increased risk could give Washington second thoughts about intervening in a hypothetical clash in the Taiwan Strait or the South China Sea, lest Beijing retaliate by attacking Americans on U.S. soil.

James Acton at the Carnegie Endowment for International Peace argues that these weapons will not significantly alter the Sino-American military balance right away, given that "the U.S. has long been vulnerable to Chinese nuclear attack."

"We will continue to be vulnerable to Chinese nuclear attack, and this does not change anything," he said.

Beijing worries that the U.S. could make a future "technological breakthrough" and develop missile defenses that could block Chinese intercontinental ballistic missiles, according to Acton.

"All nuclear weapon states are always very pessimistic about assessing their adversaries' capabilities," he said. "And I think China is just doing classic worst-case thinking and is ensuring that, even in the very, very worst case possible, it will continue to have the ability to penetrate U.S. defenses."

David Ochmanek of RAND Corp. said that "hypersonic missiles in the theater, conventionally armed, are a new problem because it's more difficult to shoot them down" than a standard ballistic missile or a cruise missile.

"When we send an aircraft carrier out to sea, it's accompanied by two or three very capable surface combatants, like your Aegis ships in the Japanese navy," he said. "And they can shoot down ballistic and cruise missiles, in limited numbers. While the hypersonic missile is more difficult to intercept, because you get less warning time, it can maneuver, its course is less predictable, and so in that way it poses a greater threat to our surface ships than the standard missiles that the Chinese have so many of now. We would like to have hypersonic missiles for the same reason."

Medium-range hypersonic weapons could contribute to Beijing's anti-access/area denial strategy, which aims to keep American forces as far as possible from the mainland. China already has hypersonic missiles with a range of around 2,000 km in service, according to the Center for Strategic and International Studies.

The Pentagon aims to deploy medium-range hypersonic weapons of its own around 2025.

Ochmanek sees these being effective in the event of an attempted Chinese landing operation in Taiwan, where speed would be of the essence. China would likely try to complete an invasion before Washington had a chance to intervene, and American forces would have a relatively short window to step in to hold them off.

The warnings by top U.S. military brass also serve to make the case for a larger military budget as the Biden administration reviews its nuclear posture. Liberal Democrats have pushed back on the idea of massive spending on a new generation of ICBMs and urged Biden to adopt a no-first-use policy for nuclear weapons -- a position at odds with current military strategy.

On the U.S. side, Beijing's hypersonic weapons test this summer has been confirmed publicly only by uniformed officials. When asked Wednesday about Milley's comments, Pentagon press secretary John Kirby referred reporters to Milley's staff.