The United States has seen no evidence of looming Chinese military activity against Taiwan, White House national security spokesman John Kirby said on Friday when asked about a possible visit to the island by US House of Representatives Speaker Nancy Pelosi.

"(We've) seen no physical, tangible indications of anything untoward with respect to Taiwan," Kirby told reporters. Pelosi has not confirmed a potential trip to Taiwan.

Tensions around Taiwan were a dominant topic on Thursday in a phone call between US President Joe Biden and Chinese President Xi Jinping. Xi warned against playing with fire over Taiwan.

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John Kirby, US national security council spokesman. Photo: Bloomberg alt=John Kirby, US national security council spokesman. Photo: Bloomberg>

China has been stepping up military activity around Taiwan seeking to pressure the democratically elected government there to accept Chinese sovereignty. Taiwan's government says only the island's 23 million people can decide their future, and while it wants peace, it will defend itself if attacked.

Pelosi, who as House speaker is number three in the line of US power hierarchy after Biden and Vice-President Kamala Harris, signalled on Friday she was going on a trip to Asia.

She did not say she was going to Taiwan.

"I'm very excited, should we go, to the countries that you'll be hearing about along the way," she said, after citing the importance of the US-Asia-Pacific relationship.

The White House has refused to comment on reports that she will go to Taiwan.

"Where she's going and what's she's going to be doing, that's for the speaker to talk to," Kirby told reporters.

Kirby said US officials have seen bellicose rhetoric from China about a potential trip by Pelosi and said, "there's no need for that".

Meanwhile, US Secretary of State Antony Blinken on Friday voiced hope of managing differences over Taiwan with China.

Asked about the trip by Pelosi, Blinken did not comment directly but said Biden made clear in a call on Thursday to Xi that the United States "strongly opposes any unilateral efforts" to change the status quo on Taiwan.

"We have many differences when it comes to Taiwan, but over the past 40-plus years, we have managed those differences and done it in a way that has preserved peace and stability and has allowed the people on Taiwan to flourish," Blinken said, referring to the period since the US switched recognition from Taipei to Beijing.