Taiwan's leader Tsai Ing-wen met with U.S. House Speaker Kevin McCarthy during a stopover in California on Wednesday in a high-profile visit condemned by Beijing as a diplomatic provocation.

Tsai, who attended a bipartisan meeting held by McCarthy at the Ronald Reagan Presidential Library outside of Los Angeles, warned that "democracy is under threat" as she spoke alongside the U.S. speaker in his home state.

"It is no secret that today the peace we have maintained and the democracy which we have worked hard to build are facing unprecedented challenges," Tsai said.

"We once again find ourselves in a world where democracy is under threat and the urgency of keeping the beacon of freedom shining cannot be understated."

Speaking to the press, McCarthy said he had a "very productive discussion" with the Taiwanese leader.

"Based on our conversation, it's clear several actions are necessary: first we must continue arms sales to Taiwan and make sure such sales reach Taiwan on a very timely basis," the top Republican said.

He went on to say that Washington must strengthen its "economic cooperation, particularly with trade and technology" and that it must continue to promote "shared values on the world stage."

Tsai stopped in the U.S. on her return from Central America, where she met with the leaders of Guatemala and Belize. The White House insists her time in the U.S. is not an official visit.

Beijing had condemned the U.S. stop, as it regards Taiwan as part of China and it rejects any official contact between countries and Taipei.

China has also raised the prospect of taking the island by force if necessary, with the U.S. threatening to take action if that happens. Taiwan is self-governing and sees itself as independent.

Asked about the visit in Brussels earlier Wednesday, U.S. Secretary of State Antony Blinken warned Beijing not to use Tsai's stopover "as an excuse to take any actions to ratchet up tensions."

Such "transits" by Taiwanese officials are "nothing new," he said.