China had warned that the United States will "pay the price" if House Speaker Nancy Pelosi visits Taiwan during her Asia trip.
US House Speaker Nancy Pelosi has landed in Taiwan brushing aside warnings from China and Russia.
With her arrival in Taipei on Tuesday, Pelosi becomes the highest-ranking American official to visit the self-ruled island that is claimed by China in 25 years.
"Our congressional delegation's visit to Taiwan honours America's unwavering commitment to supporting Taiwan's vibrant democracy," Pelosi said in a statement moments after her plane landed.
Pelosi said her trip "in no way" contradicted official US policy, which recognises "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 spokesperson John Kirby rejected Beijing's sharp criticism of the visit, saying it was not the first by a US lawmaker to Taiwan.
Earlier, live television images showed the 82-year-old lawmaker, who flew on a US military aircraft into Taipei Songshan Airport, being greeted on arrival by foreign minister Joseph Wu.
Pelosi will meet Taiwanese President Tsai Ing-wen and lawmakers, Taiwanese media reported.
Her visit has triggered increased tensions between China and the United States.
The Chinese foreign ministry said in a statement that Pelosi's trip was "extremely dangerous".
Officials in Taiwan said more than 20 Chinese military planes flew into Taiwan's air defence zone on Tuesday.
Earlier, China vowed to launch "targeted military actions" in response to Pelosi's visit.
"The Chinese People's Liberation Army is on high alert and will launch a series of targeted military operations to counter this, resolutely defend national sovereignty and territorial integrity, and resolutely thwart external interference and 'Taiwan independence' separatist attempts," defence ministry spokesperson Wu Qian said in a statement condemning the visit.
China had warned that the United States will "pay the price" if Pelosi visits Taiwan during her Asia trip.
Russia calls visit 'pure provocation'
“This tour and a possible visit to Taiwan is a pure provocation,” Kremlin spokesperson Dmitry Peskov told reporters in the capital Moscow on Tuesday.
Accusing the US of choosing “the path of confrontation,” he asserted that the potential visit is increasing the tension in Asia-Pacific Rim.
“We want to emphasise once again that we are absolutely in solidarity with China, whose attitude towards the problem is understandable and absolutely justified,” Peskov said.
The Biden administration did not explicitly urge her to call it off, while seeking to assure Beijing it would not signal any change in US policy on Taiwan.
'Playing with fire'
Moments before her arrival, Chinese state media announced advanced Su-35 fighter jets were crossing the Taiwan Strait. The brief report had no details on timing or precise location of the crossing.
While Taiwanese officials are mum on the visit, China, which claims the self-governing island as a part of its territory, has said its military "won't sit by idly" if its "sovereignty and territorial integrity" is threatened.
It has held several military drills near Taiwan since the speculations on the visit began.
Last week, China’s President Xi Jinping told his US counterpart Joe Biden "not to play with fire" over Taiwan.