The warning came from Michael Schiffer, deputy assistant defense secretary for East, during a media briefing on the annual report on military developments in China, prepared by the defense secretary for Congress.
Schiffer said China's expanding military capabilities may allow it to contribute to activities such as international peacekeeping and fighting piracy, the defense department's transcript reported.
"However, the pace and scope of China's sustained military investments have allowed China to pursue capabilities that we believe are potentially destabilizing to regional military balances, increase the risk of misunderstanding and miscalculation, and may contribute to regional tensions and anxieties," he said. "Such capabilities could increase Beijing's options for using military force to gain diplomatic advantage, advance its interests or resolve military disputes -- resolve disputes in its -- in its favor."
This year's report includes new sections on China's evolving maritime strategy and growing military involvement and engagement with other countries.
Schiffer stressed the United States welcomes a "strong, prosperous and successful China that ... enhances security and peace both in the Asia-Pacific Region and around the globe."
But he stressed the "logic" of sustained and reliable (bilateral) military-to-military dialogue to "gain the sort of transparency and strategic understanding that's necessary to forge that positive, cooperative, and comprehensive relationship."
On China's sea trial this month of its first aircraft carrier, Schiffer said the vessel could "become operationally available to China's navy by the end of 2012" but it would take additional years for an air group to achieve minimal level of combat capability aboard the carrier.
He said China continues to invest heavily in undersea warfare, with a mixture of nuclear and conventionally powered submarines. He said the People's Liberation Army has completed construction of a major naval base on Hainan Island large enough to accommodate a mix of ballistic missiles, submarines and large surface combatants, including aircraft carriers.
Commenting on the Pentagon report, U.S. Rep. Howard P. "Buck" McKeon, R-Calif., chairman of the House Armed Services Committee, said China's "increasing assertiveness and military capabilities particularly China's ability to deny access to the western Pacific" is of growing concern both to the United States and China's neighbors, CNN reported.
McKeon said China believes "it can capitalize on the global financial crisis, using the United States' economic uncertainty as a window of opportunity to strengthen" its economic, diplomatic, and security interests."
China's state-run Xinhua news agency said the Pentagon report overlooked China's "peaceful defense policy."