"Our congressional delegation's visit to Taiwan honors America's unwavering commitment to supporting Taiwan's vibrant democracy," the most senior US legislator said in a statement moments after her plane landed.

Pelosi, the highest-ranked elected US official to visit Taiwan in 25 years, said her trip "in no way" contradicted official US policy, which recognizes "one China" and has not officially recognised Taiwan as an independent state.

However, she said, "America's solidarity with the 23 million people of Taiwan is more important today than ever, as the world faces a choice between autocracy and democracy."

"The United States continues to oppose unilateral efforts to change the status quo," she added, in a reference to Beijing's pressure on Taipei to rejoin the mainland.

White House spokesman John Kirby rejected Beijing's sharp criticism of the visit, saying it was not the first by a US lawmaker to Taiwan.

The Chinese foreign ministry said in a statement that Pelosi's trip was "extremely dangerous".

"There's no violation of any sovereignty issues here," Kirby told CNN shortly after Pelosi stepped onto Taiwan soil.

"There is no reason for this to erupt into conflict. There's no change to our policy. This is absolutely consistent with it," Kirby said.

Kirby played down the news that Chinese fighter jets crossed the Taiwan Strait toward the island shortly before Pelosi's plane landed.

"The United States is not going to be intimidated by threats," he said.

"We have serious security commitments in the region.. . We take those commitments seriously", he added, saying Washington would ensure that Pelosi had a "safe and secure visit".