US President Joe Biden and China's leader Xi Jinping are expected to talk on Thursday, a source familiar with the planning said, amid fresh tensions over Taiwan and Russia's invasion of Ukraine.

White House national security spokesperson John Kirby told reporters on Tuesday that managing economic competition between the two countries would also be a focus of the call.

It will be the fifth call between the leaders, and comes as China has delivered heightened warnings to the Biden administration about a possible visit by US House Speaker Nancy Pelosi to democratically governed Taiwan, which Beijing claims as its territory.

"Everything from the tensions over Taiwan, to the war in Ukraine, as well as how we better manage competition between our two nations, certainly in the economic sphere," Kirby said of the topics to be discussed.

"This is a call that has been scheduled for a long time and there's already a pretty robust agenda of things for these two leaders to talk about," he said.

Under its one-China policy, the United States does not have official diplomatic relations with Taiwan, but is bound by US law to provide the island with the means to defend itself. The White House has been quick to reiterate that stance has not changed despite speculation over a possible trip by Pelosi.

Kirby said that Pelosi is in the line of succession to the presidency and as such, her overseas travel was a matter of US national security. But only she could make decisions about her travel.

"Bellicosity" in rhetoric from Beijing over the potential trip only escalates tensions, he said.

"We find that unhelpful and certainly not in the least bit necessary given the situation," he said.

The administration has been debating whether to lift some tariffs on Chinese goods as a way to boost the US economy, but Kirby said a decision was not expected ahead of the call.

The call comes as the US Congress considers legislation known as the CHIPs act to provide about US$52 billion (RM231 billion) in subsidies for the US semiconductor industry, as well as an investment tax credit for chip plants estimated to be worth US$24 billion, which Biden has urged as crucial for competing with China economically.

Biden referred to the planned call with Xi during virtual remarks urging passage of the legislation on Monday, telling reporters, "That's my expectation, but I'll let you know when that gets set up."

The Senate is expected to vote on final passage in coming days and the US House could follow suit as soon as later this week.

'Provocations’

The prospect of Pelosi's trip is only one in a long list of disagreements plaguing frayed US-China relations.

Earlier on Tuesday, senior US officials accused China of increased "provocations" against rival territorial claimants in the South China Sea and said "aggressive and irresponsible behaviour" by Chinese ships and aircraft meant it was only a matter of time before a major incident or accident.

A trip by Pelosi would be the first by a House speaker since 1997, and China has said it is prepared to take strong measures in response.

Daniel Russel, who served as the top US diplomat for Asia under former President Barack Obama, said the Taiwan issue had the makings of a real crisis, without any US-China mechanism to prevent that from escalating into conflict.

He said it was not clear how much pressure the Biden administration was exerting on Pelosi, but Xi was likely to push hard on the issue in the call, and added: "We are in a high-risk moment and it behoves leaders in both countries to tread carefully."

Nonetheless, Craig Singleton, a senior China fellow at the Washington-based Foundation for Defense of Democracies, said Xi would likely seek to project calm as he faces a slowing economy under pressure from strict domestic Covid-19 measures ahead of a key Communist Party Congress in the fall.

"While Xi will be clear and direct in raising China's objections about Speaker Pelosi's trip, he will probably not allow that one issue to derail the entire conversation, as doing so would further complicate his already difficult governing agenda," Singleton said.

- Reuters