SINGAPORE — Defense Secretary Donald Rumsfeld said today that the rapid development of China's missile capabilities, air force and navy put Asia's military balance at risk, and that the Pentagon believes Beijing's buildup has been far more extensive than its leaders have admitted.

In his most blunt assessment to date about the global implications of China's efforts to build a state-of-the-art arsenal, Rumsfeld warned that the expansion threatens not only the delicate situation between China and Taiwan but also the strategic equilibrium in a region increasingly vital to U.S. interests.

Speaking to Asian defense ministers at an annual security conference, the defense secretary disclosed details about an upcoming Pentagon report on China, which has the world's third-largest defense budget and the largest military budget in Asia. "China appears to be expanding its missile forces, allowing them to reach targets in many areas of the world, not just the Pacific region, while also expanding its missile capabilities here in the region," Rumsfeld said. "Since no nation threatens China, one must wonder: Why this growing investment?"

Rumsfeld's remarks seem to be an opening salvo in what could become a public, high-level debate about the threat a modern Chinese military poses to the global balance of power.

He drew an immediate response from Cui Tiankai, director of the Chinese Foreign Ministry's Asian Bureau, the top Chinese official at the conference.

"Do you truly believe that China is under no threat whatsoever from any part of the world?" Cui asked. "And do you truly believe that the United States feels threatened by the so-called emergence of China?"

Rumsfeld replied that he knew of no nations that threaten China, and that the United States does not itself feel threatened by China's growing power.

At the same time, Rumsfeld said, the Chinese military deployments in the region — especially those aimed against Taiwan — are undeniable.

With a network of bases throughout the Pacific, the United States has long enjoyed military supremacy in the region. Yet U.S. officials worry that China's military spending spree could challenge this, eventually giving Beijing the upper hand not only in its decades-long conflict with Taiwan but also in its relations with other Asian powers such as Japan, South Korea, India and Pakistan. The military progress the world's most populous country has made has long been a concern of the Bush administration.

Besides having the largest nuclear arsenal in Asia and a stable of medium- and long-range ballistic missiles, China also has the world's largest army — approximately 2.5 million men.

Some attending the conference today said Rumsfeld's posture was likely to be interpreted throughout Asia as a more combative U.S. stance toward China.

"I think the real concern that you're going to see coming out of this conference is that somehow the United States and China are heading into a period where they will be at loggerheads," said Kurt Campbell of the Washington-based Center for Strategic and International Studies, a former Pentagon official in charge of Asia policy during the Clinton administration. "I'm not sure that the battlefield has been prepared in Asia for such a message."

Chinese analysts and government officials have stressed that China has no intention of threatening its neighbors or disturbing regional stability. Its mission, they add, is to develop a credible deterrent so Taiwan doesn't declare independence.