The pace and scope of China's modernisation of its strategic forces and other surprising military developments could pose a credible long-term threat to the United States, the Pentagon warned Tuesday.
In an annual report to Congress, the Defence Department said China's ability to sustain military power at a distance is limited but it has the greatest potential of any nation to compete militarily with the United States.
"Long-term trends in China's strategic nuclear forces modernisation, land- and sea-based access denial capabilities, and emerging precision-strike weapons have the potential to pose credible threats to modern militaries operating in the region," the report said.
"Several aspects of China's military development have surprised US analysts, including the pace and scope of its strategic forces modernisation," an executive summary of the report said.
"China's military expansion is already such as to alter regional military balances," it added.
"Long-term trends in China's strategic nuclear forces modernisation, land- and sea-based access denial capabilities, and emerging precision-strike weapons have the potential to pose credible threats to modern militaries operating in the region," the report said.
The annual China military power report is a closely watched barometer of military relations between the Asian power and the United States, the dominant military power in the Asia Pacific Region.
The report made waves last year by calling attention to big, unacknowledged increases in Chinese spending on a major military build-up that it said put at risk the military balance in the region.
The latest report expanded on that theme and said China had still not adequately explained "the purposes or desired end-stats of their military expansion."
"Absent greater transparency, international reactions to China's military growth will understandably hedge against these unknowns," the report said.
In the near term, China's military build-up appeared focused on preparing for contingencies in the Taiwan Strait, including the possibility of US intervention, the report said.
China now has an estimated 710 to 790 short-range missiles opposite Taiwan, according to the report.
"However, analysis of China's military acquisitions suggest it is also generating capabilities that could apply to other regional contingencies, such as conflicts over resources or territory," it said.
It said China has developed a new doctrine for modern warfare, reformed military institutions and personnel systems, improved exercises and training, and acquired advanced foreign and domestic weapons systems.
The report discusses China's acquisition of Russian transport and air refuelling aircraft and its interest in acquiring the SU-33, a Russian-made maritime strike aircraft capable of operating from aircraft carriers.