STORY: The U.S. Speaker of the House of Representatives arrived in Taiwan late on Tuesday aboard a U.S. Air Force jet.
The visit comes after fierce and repeated warnings and condemnations over the the potential trip from Beijing, which views the self-governed island as a breakaway Chinese province.
In a statement from Speaker Nancy Pelosi tweeted shortly after landing, she wrote: "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 visit by the speaker has pushed relations between Washington and Beijing to a new low.
China views visits by U.S. officials to Taiwan as sending an encouraging signal to the pro-independence camp on the island.
Chinese Foreign Minister Wang Yi said on Tuesday that U.S. politicians who "play with fire" on the Taiwan issue will "come to no good end".
Pelosi's visit comes as part of a tour across Asia, including stops in Singapore and Malaysia.
Washington has asserted Pelosi has every right to visit Taiwan, and decried what it described as Chinese sabre-rattling and warned Beijing against the risk of unnecessary escalation.
But Chinese warplanes buzzed the line dividing the Taiwan Strait on Tuesday, shortly before Pelosi arrived in Taipei.
Meanwhile four U.S. warships, including an aircraft carrier, were positioned in waters east of Taiwan on what the U.S. Navy called routine deployments.
Washington has no official diplomatic relations with Taiwan but is bound by U.S. law to provide the island with the means to defend itself.
A source told Reuters most of Pelosi's planned meetings, including with Taiwan's President Tsai Ing-wen, were scheduled for Wednesday.