The Chinese defense minister threatened on Thursday that the military would move "at any cost" to thwart attempts to separate the self-governing island of Taiwan, which Beijing says belongs to it.
The United States has angered China over its recent sanctions against the Chinese military, one of a number of hot issues in relations between the two countries.
Other notable cases include the bitter trade war between the two countries, as well as the strengthening of Taiwan and China for their military status in the South China Sea.
On Monday, the United States sent two warships across the Taiwan Straits in its second such operation this year, the latest in a string of gestures by the White House in support of Taiwan's democracy.
"The Taiwan issue is linked to China's sovereignty and territorial integrity and touches on China's fundamental interests," Chinese Defense Minister Wei Feng He said at the opening of the Xiangshan Forum in Beijing.
"If China tries to separate Taiwan from China, the Chinese military will take the necessary measures at any cost," he said.
Relations between China and Taiwan have deteriorated since President Tsai Ing-wen, a pro-independence Democratic Progressive Party, took power in 2016.
Wei said China's military relations with the United States were important and sensitive, but at the same time he stressed that China would never give up an inch of its territory.
China considers Taiwan a rogue province and has never ruled out the use of force to subjugate the Democratic-ruled island to its control.
Beijing this year stepped up military and diplomatic pressure, carried out air and naval exercises around the island and convinced three of the few governments that still support Taiwan to stop this support.
