China usually criticises the annual Pentagon report
Beijing has reacted angrily to a Pentagon report on China's military power, which claimed it was altering the military balance in Asia.
A foreign ministry spokesman called it a "gross distortion of the facts", and urged an end to "Cold War thinking".
In its annual report to Congress, the Pentagon said China was developing "disruptive" technologies for nuclear, space and cyber warfare.
It could be used to enforce claims over disputed territories, the report said.
Beijing was again criticised for a lack of transparency in reporting military spending and security policy.
"This report issued by the US side continues to play up the fallacy of China's military threat," Foreign Ministry spokesman Qin Gang told journalists.
He said Beijing had complained to Washington about it, and urged the US to "drop the Cold War thinking... to prevent further damage to the relationship between the two countries and two armies".
Tensions were heightened earlier this month after a confrontation between US and Chinese ships in China's exclusive economic zone south of Hainan, during which China accused the US of spying.
The Pentagon reported that China was successfully managing to expand its arsenal of sophisticated weaponry, even though Beijing's ability to sustain military power at a distance remains limited.
Chinese "armed forces continue to develop and field disruptive military technologies", including "nuclear, space, and cyber warfare".
Some of these developments help China to participate in international peacekeeping, humanitarian and counter-piracy missions, the report acknowledged.
But they could also allow China to "project power to ensure access to resources or enforce claims to disputed territories," it said.
The Pentagon analysis said China was developing weapons that would disable its enemies' space technology such as satellites, boosting its electromagnetic warfare and cyber-warfare capabilities and continuing to modernise its nuclear arsenal.
It also noted a build-up of short-range missiles opposite Taiwan, despite a significant reduction in tension between the two in recent months.
And while the report also welcomed the rise of a peaceful, stable and prosperous China, it added: "Much uncertainty surrounds China's future course, particularly regarding how its expanding military power might be used."
The report estimated China's military spending in 2008 was roughly double that of a decade ago.
Beijing insists its increased military spending is purely for defensive purposes and is still small in comparison with that of the US.
China has repeatedly said that the Pentagon's annual report on its military power unfairly portrays China as a military threat when it is committed to a "peaceful rise" as its economic power grows.
China's armed forces are undoubtedly undergoing a dramatic transformation from a poorly-equipped peasant army to an increasingly sophisticated modern military, the BBC's defence and security correspondent Rob Watson says.
But its level of training and co-ordination as well as actual war fighting capability is still in doubt, he adds.