The claim to Taiwan, which split with the mainland in 1949, is an "insurmountable red line," Wang Yi said at a news conference on Sunday during the annual meeting of China's ceremonial legislature.

The United States has no official relations with Taiwan but extensive informal ties. Trump irked Beijing by sending Cabinet officials to visit Taiwan in a show of support.

"The Chinese government has no room for compromise," Wang said.

"We urge the new US administration to fully understand the high sensitivity of the Taiwan issue" and "completely change the previous administration's dangerous practices of 'crossing the line' and 'playing with fire,"' he said.

Biden says he wants a more civil relationship with Beijing but has shown no sign of softening Trump's confrontational measures on trade, technology and human rights.

Surveys show American public attitudes turning more negative toward China, which is seen as an economic and strategic competitor.

Wang gave no indication how Beijing might react if Biden doesn't change course, but the ruling Communist Party has threatened to invade if Taiwan declares formal independence or delays talks on uniting with the mainland.

The State Department later reiterated that the Biden administration's support for Taiwan was rock-solid and that the US stood with its regional friends and allies, including "deepening our unofficial ties with democratic Taiwan".

"We urge Beijing to cease its military, diplomatic, and economic pressure against Taiwan and instead engage in meaningful dialogue with Taiwan's democratically elected representatives," said the statement on Sunday in Washington.

Wang's comments in a wide-ranging, two-hour news conference reflected Beijing's increasing assertiveness abroad and rejection of criticism over Hong Kong, the northwestern region of Xinjiang and other sensitive topics.

Australian Associated Press