China's top envoy in Washington on Tuesday lodged a "stern demarche and strong protest" to the US on House Speaker Nancy Pelosi's visit to Taiwan, which he blasted as "reckless and provocative", as foreign policy observers weighed in on the risks generated by the trip.

Disregarding China's strong opposition, Pelosi flew to Taiwan late Tuesday in a serious flouting of the one-China principle and the provisions of the three China-US joint communiqués.

"The speaker's visit is a major event upgrading the negative movement of the US side on the Taiwan question...  and sends a very wrong signal to 'Taiwan independence' separatist?forces," Ambassador Qin Gang said, according to a statement from the embassy.

"Egregious in nature, the visit has caused extremely serious damage and carries extremely bad influence. China strongly condemns and protests against it," he said.

Qin noted that China firmly urges the US side to stop playing the "Taiwan card" and using Taiwan to contain China, immediately correct its mistake, manage and eliminate the pernicious impact of Pelosi's visit, and refrain from further taking dangerous and provocative moves to infringe on China's sovereignty and security.

The US side should also adopt real actions to honor US President Joe Biden's "five no's" commitment, he said.

The embassy statement did not specify the "five no's". They generally refer to Biden's  reiteration that the US does not seek to have a new Cold War with China, to change China's system, or to revitalize alliances against China, and that the US does not support "Taiwan independence" or intend to seek a conflict with China.

Qin noted that Pelosi is the No 3 person in the US government after the president and vice-president. 

"Now having the third highest-ranking official in its government visit Taiwan to provoke China. Where is the US commitment to the one-China principle and the provisions of the three Sino-US Joint Communiques? Where is the US commitment of not supporting 'Taiwan independence'?" Qin said.

Facts have proved that it is the US side, not others, that has reneged on its commitments, triggered the crisis and undermined peace and stability across the Taiwan Straits, the ambassador said, according to the statement. 

In an interview with CNN on Tuesday, Qin said Pelosi's visit is a "reckless, provocative move" that deals a serious blow to the political foundation of China-US relations, and seriously infringes on China's sovereignty and territorial integrity.?

"The current situation is created purely by the US side, and so of course it has to bear the responsibility," he said. "We will take whatever we can to safeguard our sovereignty and territorial integrity. And our response will be very firm, strong and forceful."

Qin said that the question of Taiwan is not about democracy.

"It is the aspiration of the more than 1.4 billion Chinese people to achieve the reunification of China, and it is an unbending will of the whole Chinese nation to defend our national sovereignty and territorial integrity," he said.

The Democratic speaker is the highest-ranking American official in 25 years to visit the island since Newt Gingrich did as House speaker in 1997. The 1990s visit was wrong and firmly opposed by China, Qin said.

"The one mistake cannot justify the following mistakes in the same nature," he added.

Michael D. Swaine, director of the East Asia Program at the Quincy Institute for Responsible Statecraft, a think tank in Washington, said on Tuesday that US officials can "talk until they're blue in the face" over not supporting Taiwan independence.  

In a series of comments posted on Twitter, Swaine said China believes that the US officials' actions belie their words and regards the Pelosi trip as a "major betrayal of past limits".

Nicholas Hope, the director of the Stanford Center for International Development, said he had "fervently" hoped that Pelosi was wise enough to avoid going to Taiwan. 

"Going there would exacerbate the already delicate state of China-US relations and, I believe, would be in the interests of neither country, nor those of Taiwan," Hope told China Daily.

"Taiwan will not be more secure or more prosperous as a result of this purely symbolic visit, and a lot of bad things could happen," wrote New York Times columnist Thomas Friedman on Monday.

"It is a measure of our political dysfunction that a Democratic president cannot deter a Democratic House speaker from engaging in a diplomatic maneuver that his entire national security team — from the CIA director to the chairman of the Joint Chiefs — deemed unwise," he wrote.

In a piece titled, "Would You Go to War So Nancy Pelosi Can Visit Taiwan?", Peter Beinart wrote on substack.com: "If her visit sparks a Chinese military response, and brings Washington and Beijing to the brink of war, will they (Washington politicians) enlist their kids to fight?

"It's the kind of question foreign policy commentators rarely ask. It's too impolite. And when it comes to the China debate in Washington, it's this politeness—the failure to talk in blunt, human terms about the consequences of war — that terrifies me," wrote Beinart, editor-at-large at Jewish Currents, a CNN contributor and also a CUNY journalism professor.

"Could a war over Taiwan blow up the entire world? Yes. There are few Americans who know China better than J. Stapleton Roy and Chas Freeman. Roy grew up there and later returned as US ambassador. Freeman served as interpreter when Richard Nixon visited China in 1972. Both have recently warned that a conflict over Taiwan could escalate into nuclear war," Beinart said.

"How many lives are worth risking so Nancy Pelosi can visit Taiwan? It's an impolite question — one that in the coming days the US media should ask again and again."

Ted Galen Carpenter, a senior fellow in defense and foreign policy studies at the Cato Institute, wrote on antiwar.com on Tuesday: "In many ways, Washington's determination to press ahead with greater support for Taiwan as part of an overall containment policy directed against China is reminiscent of the blunders US officials made with respect to NATO expansion, especially the campaign to incorporate Ukraine, and Washington's tone-deaf response to Moscow's escalating complaints.

"The administration must implement a quiet retreat regarding its growing political and military ties to Taipei and adopt a less confrontational approach to Beijing,"  Carpenter said. 

"It has become increasingly obvious to PRC leaders that the United States is pursuing a full-blown anti-China containment policy, with Taiwan as the point of the spear, in a desperate effort to preserve Washington's fading strategic primacy in East Asia. 

"It is highly unlikely that Beijing will passively accept such an intrusive US presence in China's core security sphere over the long term. As the PRC's economic and military power continues to grow, Beijing's resistance to Washington's hegemonic efforts will escalate," he said.

Chang Jun in San Francisco contributed to this story.