China's foreign minister has warned the Biden administration to roll back former US President Donald Trump's "dangerous practice" of showing support for Taiwan, the island democracy claimed by Beijing as its own territory.

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

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

"The Chinese government has no room for compromise," Mr 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.

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

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

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

Mr 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 north-western region of Xinjiang and other sensitive topics.

He defended proposed changes in Hong Kong that will tighten Beijing's control by reducing the role of its public in government, and dismissed complaints that they will erode the autonomy promised to the former British colony when it returned to China in 1997.

The changes announced on Friday follow the arrest of 47 pro-democracy figures in Hong Kong under a national security law imposed last year following months of anti-government protests.

Beijing needs to protect Hong Kong's "transition from chaos to governance", Mr Wang said.

The proposal would give a pro-Beijing committee a bigger role in picking Hong Kong legislators, which would be a marked reduction of democracy and Western-style civil liberties in Hong Kong.

Mainland officials say they want to make sure the territory is controlled by people deemed patriots.

"No-one cares more about the development of democracy in Hong Kong than the central government," Mr Wang said.

He said the changes will protect the "rights of Hong Kong residents and the legitimate interests of foreign investors".

Also on Sunday, Mr Wang rejected complaints that Beijing's treatment of predominantly Muslim ethnic minorities in Xinjiang amounts to genocide.

Human rights researchers say more than one million people, many of them members of the Uighur minority, have been sent to detention camps. Chinese officials say they are trying to prevent extremism.

"The so-called existence of genocide in Xinjiang is absurd. It is a complete lie fabricated with ulterior motives," Mr Wang said.

He blamed "anti-China forces" which, he said, want to "undermine the security and stability of Xinjiang and hinder China's development and growth".