Simi Valley (United States) (AFP) - US House Speaker Kevin McCarthy met Taiwan’s president in California on Wednesday for talks that have already prompted outrage and dire warnings from China.

The Republican leader shook hands warmly with Tsai Ing-wen, on what is technically a stop-over after her trip to Latin America to visit two of Taiwan’s dwindling band of official diplomatic allies.

“I’m optimistic that we will continue to find ways for the people of America and Taiwan to work together to promote economic freedom, democracy, peace and stability in Asia,” McCarthy said as the two posed for pictures.

Duelling demonstrations from both pro-Beijing and pro-Taipei camps gathered at the Ronald Reagan Presidential Library in Simi Valley for Tsai’s arrival, while a small plane flew overhead trailing a banner that read: “One China! Taiwan is part of China!”

China views Taiwan as part of its territory and has vowed to one day seize it, by force if necessary. Beijing balks at any official contact Taipei has with other countries.

This week, it warned McCarthy, a California native who is second in line to the US presidency, that he was “playing with fire” by meeting Tsai.

“China is strongly opposed to the US arranging for Tsai Ing-wen to transit through its territory, and is strongly opposed to the meeting between House Speaker Kevin McCarthy, the third-ranking US official, and Tsai Ing-wen,” foreign ministry spokeswoman Mao Ning told reporters.

“It seriously violates the One-China principle… and seriously undermines China’s sovereignty and territorial integrity.”

Taiwan is a flourishing democracy, with its own military, an independent judiciary and all the trappings of a fully functioning state.

But only a handful of countries acknowledge it as a sovereign nation.

Under a carefully constructed diplomatic fudge, the United States formally recognizes authoritarian Beijing, but is an important backer of Taiwan, and maintains strong unofficial ties.

Taipei enjoys bipartisan support in the US Congress, and has grown closer to Washington under Tsai’s leadership – much to China’s annoyance.

US Secretary of State Antony Blinken played down the significance of Tsai’s stop in California, and cautioned Beijing against using it as an “excuse to ratchet up tensions.”

“These transits by high level Taiwanese authorities are nothing new,” he told reporters in Brussels, where he was meeting with NATO foreign ministers.

“They are private and unofficial.”

- ‘Resolve to defend ourselves’ -

Last year, McCarthy’s predecessor, Democrat Nancy Pelosi sparked fury in Beijing by becoming the most senior US politician to visit the island in over two decades.

That prompted Beijing to launch its largest-ever military exercises in waters around Taiwan.

McCarthy had originally planned to go himself, but opted instead to meet Tsai in California.

The decision was viewed as a compromise that would underscore support for Taiwan but avoid inflaming tensions with China.

His office said that the meeting would be “bipartisan,” while US media reported that more than a dozen other members of Congress would attend.

Tsai’s stop in southern California comes after trips to Guatemala and Belize and after a brief stop in New York last week, where she was greeted by flag-waving Taiwanese expatriates.

“We have demonstrated a firm will and resolve to defend ourselves, that we are capable of managing risks with calm and composure and that we have the ability to maintain regional peace and stability,” she said in New York.

Bonnie Glaser, managing director of the Indo-Pacific Program at the German Marshall Fund, said China had been outspoken about the visit in recent days, and may feel that it has to keep up the rhetoric.

“China has already said some fairly threatening things which suggests to me that they have to respond in some way,” she told AFP, adding that “otherwise (President) Xi Jinping could end up looking weak.”

But China’s response will be shaped in part, Glaser said, by what McCarthy says publicly after the meeting.