China said Sunday that its one-China policy is “non-negotiable” after President-elect Donald Trump suggested that he might use American policy on Taiwan as a bargaining chip between the two sides.

China Foreign Ministry spokesman Lu Kang reiterated in a statement that the “government of the People’s Republic of China is the only legitimate government representing China.”

"That is the fact acknowledged by the international community and no one can change,” Lu added.

Since recognizing Beijing in 1979, Washington has maintained only unofficial ties with Taiwan, the self-governing island that Beijing considers its territory — a status quo that Trump has repeatedly threatened to upend since winning the November election.

Trump told The Wall Street Journal on Friday that “everything is under negotiation, including ‘one China.’” The interview is the latest indication Trump that he will shake up the U.S.-China relationship, particularly on Taiwan, which China considers a core national interest.

China had already been rattled over Trump’s call with Taiwanese President Tsai Ing-wen, the first time an American president or president-elect had publicly spoken to Taiwan’s leader in nearly four decades.

Trump then said in a television interview that he didn't feel "bound by a one-China policy unless we make a deal with China having to do with other things, including trade."

After attacking China repeatedly during his campaign, Trump has continued to disparage China on his Twitter account over its military build-up in disputed areas of the South China Sea, allegedly manipulating its currency to put American companies at a disadvantage, and not doing enough to curb North Korea's nuclear program.

He has also announced that a new White House trade council will be led by economist Peter Navarro, a sharp critic of Chinese economic policy who wrote a book titled "Death By China."

Trump told the Journal that he would not label China a currency manipulator as soon as he takes office, though he repeated his contention that China is manipulating the yuan.

So far, Beijing has reiterated its refusal to negotiate on Taiwan and to push for positive cooperation between the two sides, though state-run media have run several strongly worded editorials attacking Trump.

The Associated Press contributed to this report.