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China on Saturday rebuked president-elect Donald Trump for his recent suggestion that the longstanding U.S. "One China" policy could be changed under his administration.

Under the policy the U.S. recognizes the People's Republic of China as the sole legal government and does not have diplomatic relations with Taiwan, which China considers a renegade province. Its beginnings date to 1972 when Richard Nixon visited mainland China to initiate closer relations with the country's Communist government.

"There is only one China in the world, and Taiwan is an inalienable part of China’s territory,” Chinese Foreign Ministry spokesperson Lu Kang said in a statement posted to the ministry's website.

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Trump in an interview with the Wall Street Journal published Friday the president-elect was asked whether he supported the One China policy, and he replied: "Everything is under negotiation, including One China."

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Trump raised eyebrows about the policy last month when the president-elect spoke over the phone with Taiwan President Tsai Ing-wen. The U.S. has not had diplomatic relations with Taiwan since 1979.

Trump claimed then that he only accepted a congratulatory call. A top Taiwanese official told NBC News the call was pre-arranged. At the time, China’s foreign minister dismissed the call as "only a little trick played by Taiwan."

Related: Trump's Call With Taiwan's Leader Exposes China's Strained Relations

Saturday, Lu said the One China policy was not open to debate.

"The One China principle serves as the political foundation for the development of China-U.S. ties and is non-negotiable," he said.

"We urge the U.S. side to be fully aware of the high sensitivity of the Taiwan question and stick to the commitment made by past U.S. administrations," Lu said. He said failing to do so could lead to disruptions in "the sound and steady development of China-U.S. relationship and cooperation on key areas."