U.S. House of Representatives Speaker Nancy Pelosi is planning to visit Japan early next month, diplomatic sources said Wednesday, amid reports that she is considering a trip to Taiwan in a move almost certain to trigger an outcry from China.

Pelosi's trip to Taiwan, if realized, would be the first by a serving U.S. House speaker in 25 years. The administration of U.S. President Joe Biden has been enhancing ties with the self-ruled democratic island.

U.S. House of Representatives Speaker Nancy Pelosi. (Getty/Kyodo)

China has been increasing its pressure on Taiwan, which Beijing views as a renegade province awaiting reunification with the mainland, by force if necessary.

During her expected stay in Japan, Pelosi is likely to hold separate meetings with Prime Minister Fumio Kishida and Japan's House of Representatives Speaker Hiroyuki Hosoda, the sources said.

Russia's invasion of Ukraine and China's growing maritime assertiveness in the Pacific are among the expected topics of their talks, according to the sources.

It remains unclear whether the U.S. House speaker and an accompanying group of Democrat lawmakers intend to stop by Japan before or after a possible trip to Taiwan.

In April, Pelosi postponed her planned visit to Asia including Japan after testing positive for the coronavirus. She had also considered visiting Taiwan during the trip, according to Taiwanese and Japanese media.

Chinese Foreign Ministry spokesman Zhao Lijian told a press conference Wednesday in Beijing that China has repeatedly made clear to the United States its "stern position" against Pelosi's potential visit to Taiwan.

"We're fully prepared for any eventuality. If the U.S. side insists on making a visit, the Chinese side will take firm and strong measures to safeguard our sovereignty and territorial integrity," he said, adding that Washington "must assume full responsibility for that."

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