The White House has warned that China may respond to Nancy Pelosi`s mooted visit to Taiwan with military provocations, BBC reports.
This could include firing missiles near Taiwan, or large-scale air or naval activities, spokesman John Kirby said.
Pelosi, the US House of Representatives Speaker, is on a tour of Asia.
Taiwanese and US media outlets say she plans to visit Taipei, but this has not been confirmed by the US government.
Taiwan is a self-ruled island, but claimed by China, which sees it as a breakaway province - Beijing has warned of "serious consequences" if Pelosi goes there.
While the US maintains what it calls a "robust, unofficial relationship" with Taiwan, it has formal diplomatic ties with China, and not Taiwan.
On Monday, China`s United Nations envoy Zhang Jun warned the visit would undermine relations between Beijing and Washington, Reuters news agency reported.
There is strong bipartisan support for Taiwan among the American public and in the US Congress. And Pelosi, a senior figure in the Democratic Party, has long been a vocal critic of the Chinese leadership, denouncing its human rights record. She has previously met pro-democracy dissidents and visited Tiananmen Square to commemorate victims of the 1989 massacre.
The speaker began her tour of Asia on Sunday, with stops scheduled in Singapore, Malaysia, South Korea and Japan.
She originally planned to visit Taiwan in April, but postponed the trip after she tested positive for Covid-19.
Earlier this month Pelosi said it was "important for us to show support for Taiwan".
President Joe Biden has said the US military believes a Pelosi visit to Taiwan is "not a good idea right now".
On Monday, White House national security spokesman John Kirby said that China`s escalations could include making "spurious legal claims" in the days to come, for example by claiming that the Taiwan Strait is not an international waterway.
He said other signs indicate that Beijing may send flights towards the island, as part of a planned incursion into Taiwan`s airspace.
Kirby pointed out that Republican former Speaker of the House Newt Gingrich had visited Taiwan in 1997, and that other US lawmakers visited Taiwan earlier this year.
"Nothing has changed. There is no drama to talk to. It is not without precedent for a Speaker of the House to go to Taiwan," he said, adding that Pelosi is travelling on US military planes during her Asian tour.
Speaking at the United Nations, US Secretary of State Antony Blinken called on China to be measured in the event that Pelosi does visit.
"If the speaker does decide to visit, and China tries to create some kind of crisis or otherwise escalate tensions, that would be entirely on Beijing," he told reporters after nuclear non-proliferation talks in New York.
"We are looking for them - in the event she decides to visit - to act responsibly and not to engage in any escalation going forward."
