The Pentagon says China's military power is on the rise as it pursues more land-based missiles and attack submarines, and that the secrecy of its drive increases the risk of miscalculation.
The annual military assessment was released Monday. It comes at a time of strained U.S. relations with Beijing.
This year, the two countries have been at odds on whether North Korea attacked a South Korean warship and how to settle China's longtime dispute with Taiwan.
The Pentagon report says Beijing is actively pursuing ways to prevent the U.S. from intervening in a potential conflict with Taiwan. The report also says the country's secrecy about its military program "increases the potential for misunderstanding and miscalculation."