China’s foreign ministry says it has lodged a complaint with the US after President-elect Donald Trump spoke to Taiwan’s leader in a phone call.
China sees Taiwan as a breakaway province. US policy set in 1979 cut formal relations with Taiwan.
Mr Trump’s transition team said he and Tsai Ing-wen noted “close economic, political, and security ties”.
The US is Taiwan’s most important ally and provides Taiwan with sufficient weaponry to defend itself.
China said it had lodged a “solemn representation” with Washington.
According to the state news agency Xinhua, China urged the US “to cautiously, properly handle Taiwan issue to avoid unnecessary disturbance to Sino-US relations”.
Foreign Minister Wang Yi dismissed the call as a “petty trick” by Taiwan, Chinese state media said.