China has threatened “firm and resolute measures” if US House Speaker Nancy Pelosi makes her rumoured trip to Taiwan.

Mrs Pelosi had planned to visit the island in April, but the trip was cancelled after she tested positive for coronavirus.

Her office has not confirmed any details of a rescheduled trip, but her comments last week that it is “important for us to show support for Taiwan” have sparked rumours it could be on the cards.

She would be the highest-ranking US politician to visit the island, which China claims as part of its People’s Republic, since 1997.

It comes ahead of a phone call between Presidents Joe Biden and Xi Jinping on Thursday.

Zhu Feng, dean of the Institute of International Studies at Nanjing University in China, said Mrs Pelosi is “playing with fire”.

“This is the issue that irks China the most,” he said. “On the call both sides need to give each other a positive signal that says we can have basic trust in each other, which is especially needed as the world remains fragile and volatile.

“Not condoning Pelosi’s Taiwan visit is a prerequisite to building this trust.”

Biden insists military ‘doesn’t think it’s a good idea’

Mr Biden’s team is also thought to have discouraged Mrs Pelosi from going.

Last week he told reporters that “the military thinks it’s not a good idea”.

Beijing has not ruled out military action if the speaker does make her visit. It also consistently threatens a forced annexation of the island.

Chinese foreign ministry spokesperson Zhao Lijian said there would be “firm and resolute measures” in response to any trip.

“The US will be responsible for all of the serious consequences,” he added.

Long-awaited phone call between DC and Beijing

The phone call between the US and Chinese leaders is expected to focus on managing economic competition between the US and China, according to White House National Security spokesperson John Kirby.

But amid tensions over Chinese military build-up in the South China Sea, there are several other issues that will need to be discussed.

“Everything from the tensions over Taiwan, to the war in Ukraine,” Kirby said of which topics would be covered.

“This is a call that has been scheduled for a long time and there’s a pretty robust agenda of things for these two leaders to talk about,” he added.

The US has consistently shown support for Taiwan, but has formal relations with China – and not the island in its own right.

Six US lawmakers made a surprise visit to Taipei in April, which angered officials in Beijing.

Over her decades-long Congressional career Mrs Pelosi has repeatedly criticised China for its human rights record, among other things.