China lodged a diplomatic protest on Saturday after U.S. President-elect Donald Trump spoke by phone with President Tsai Ing-wen of Taiwan, but blamed the self-ruled island Beijing claims as its own for the "petty" move.
The 10-minute telephone call with Taiwan's leadership was the first by a U.S. president-elect or president since President Jimmy Carter switched diplomatic recognition from Taiwan to China in 1979, acknowledging Taiwan as part of "one China".
China's Foreign Ministry said it had lodged "stern representations" with what it called the "relevant U.S. side", urging the careful handling of the Taiwan issue to avoid any unnecessary disturbances in ties.
"The one China principle is the political basis of the China-U.S. relationship," it said.
The wording implied the protest had gone to the Trump camp, but the ministry provided no explanation.
Speaking earlier, hours after Friday's telephone call, Chinese Foreign Minister Wang Yi pointedly blamed Taiwan for the exchange, rather than Trump, a billionaire businessman with little foreign policy experience.
"This is just the Taiwan side engaging in a petty action, and cannot change the 'one China' structure already formed by the international community," Wang said at an academic forum in Beijing, China's Foreign Ministry quoted him as saying.
"I believe that it won't change the longstanding 'one China' policy of the United States government."
In comments at the same forum, Wang noted how quickly President Xi Jinping and Trump had spoken by telephone after Trump's victory, and that Trump had praised China as a great country.
Wang said that exchange had sent "a very positive signal about the future development of Sino-U.S. relations", according to the ministry's website. Taiwan was not mentioned in that call, according to an official Chinese transcript.
China's Taiwan Affairs Office also called the conversation a "petty" move by Taiwan that does not change the island's status as part of China. Beijing is resolute in opposing independence for Taiwan, it added.
Trump said on Twitter that Tsai had initiated the call he had with the Taiwan president. "The President of Taiwan CALLED ME today to wish me congratulations on winning the Presidency. Thank you!" he said.
Alex Huang, a spokesman for Tsai, said: "Of course both sides agreed ahead of time before making contact."