US Defense Secretary Donald Rumsfeld accused China today of enhancing its ability to project power at a time when it faced no threat and said Beijing will have to expand political freedoms to maintain economic growth and influence.
The Pentagon has been raising alarms over China's military modernisation for several years.
Mr Rumsfeld's rhetorical assault, in a speech to a conference of regional defense ministers, underscores a growing concern in the United States over China's rising military, economic and diplomatic power.
But facing an audience anxious about a possible US-China confrontation in Asia, Mr Rumsfeld toned down parts of his prepared speech and insisted Washington sought neither to destabilise China nor fan a competition for regional influence.
"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 within this region," he told an annual conference hosted by the International Institute of Strategic Studies.
"China also is improving its ability to project power, and developing advanced systems of military technology," he said.
"Since no nation threatens China, one must wonder: Why this growing investment? Why these continuing large and expanding arms purchases? Why these continuing robust deployments?"
One line dropped from the prepared text said: "One might be concerned that this buildup is putting the delicate military balance in the region at risk - especially, but not only, with respect to Taiwan."
The United States itself has vastly boosted defense spending since the September 11th attacks. Some experts say China's military increases can be expected of a growing power.
During a question and answer session, a Chinese foreign ministry official asked if Rumsfeld really believed China faced no threat and if the United States felt threatened by China. "I don't know of nations that threaten China," Rumsfeld said, adding: "No, we don't feel threatened by the emergence of China. It strikes me that the emergence of China is perfectly understandable."