China's foreign ministry on Sunday again rejected President-elect Donald Trump's suggestion that he might use American policy on Taiwan as a bargaining chip between the two sides.
Spokesman Lu Kang says the "one China" policy is "non-negotiable".
Since recognising 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.
"The government of the People's Republic of China is the only legitimate government representing China," Lu said in a statement.
"That is the fact acknowledged by the international community and no one can change."
Trump told The Wall Street Journal in an interview published on Friday that "everything is under negotiation, including 'one China'".
The interview is the latest indication by Trump that he will shake up the US-China relationship, particularly on Taiwan, which China considers a core national interest.
China was already angered by Trump's December 2 phone call with Taiwanese President Tsai Ing-wen, the first time an American president or president-elect has publicly spoken to Taiwan's leader in nearly four decades.
Beijing considers any reference to a separate Taiwanese head of state to be a grave insult.
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.
Chinese political observers on Sunday said they expect Beijing's response to change once Trump is inaugurated on Friday.
