"I have been encouraged by public statements made recently by Chinese leaders as to the seriousness of this incident and the need for accountability, and yet dismayed by a fairly tepid response to calls by the international community for support," Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said in a speech to the Asia Society.

A copy of his prepared remarks was obtained by The Washington Times.

Adm. Mullen called China a rising regional leader but criticized Beijing for failing to work together with the United States to promote regional stability.

China's recent rejection of military-to-military contact is "particularly disappointing," he said because it is preventing the chance for the two militaries to "listen and learn about each other."

However, Adm. Mullen said he is concerned by the disconnect between China's stated military intentions and its rapid military buildup of high-technology weapons, including "anti-access" weapons designed to attack U.S. warships and other weapons needed to provide security in the Asian Pacific.

China's "heavy investments of late in modern, expeditionary maritime and air capabilities seems oddly out of step with their stated goal of territorial defense," Adm. Mullen said.

"Every nation has a right to defend itself, and to spend as it sees fit for that purpose," he said. "But a gap as wide as what seems to be forming between China's stated intent and its military programs leaves me more than curious about the end result. Indeed, I have moved from being curious to being genuinely concerned."

Adm. Mullen's comments on China followed a sharp exchange between a Chinese general and Defense Secretary Robert M. Gates in Singapore last week.

Chinese Gen. Zhu Chenghu, a leader of the Chinese National Defense University, criticized Mr. Gates comments about U.S. arms sales to Taiwan, saying the weapons transfers are part of a U.S. effort to "take the Chinese as an enemy."

Gen. Zhu, who once announced that China would use nuclear weapons to retaliate against any U.S. conventional precision missile strikes, also said there are "controversial views" on who sank the South Korean ship Cheonan, despite an international investigation that concluded a North Korean submarine fired a torpedo that sank the coastal partol ship, killing 46 sailors in March.

Adm. Mullen said "the North Korean attack on a South Korean warship this spring was not only an egregious breach of the fragile peace on that peninsula, but also yet another example of the sort of provocation and pre-meditation with which the North's regime continues to isolate itself and threaten its neighbors."

"We in the United States military stand firmly by our allies in the Republic of Korea and will move forward, in keeping with international agreements, to demonstrate that solidarity in coming weeks," he said.

The admiral said U.S. military forces currently are "planning maritime exercises to sharpen skills and strengthen collective defenses."

Defense officials said one option will be to dispatch the aircraft carrier strike group headed by the USS George Washington to waters near the Korean Peninsula for the exercises.