China warned Monday it will take “strong measures” if House Speaker Nancy Pelosi visits Taiwan next month.

The Financial Times, citing several people familiar with the situation, reported last week that Pelosi plans to visit Taiwan’s capital, Taipei, in August after she was forced to postpone a trip there in April when she was diagnosed with COVID-19. 

Pelosi’s office has declined to comment, saying it does not confirm or deny the speaker’s international travel in advance, due to longstanding security protocols.

The California Democrat would be the highest-ranking American lawmaker to visit Taipei since House Speaker Newt Gingrich in 1997.

President Joe Biden told reporters last week that U.S. military officials believe it’s “not a good idea” for Pelosi to visit Taiwan, but he stopped short of suggesting she should not travel there.

On Monday, Chinese Foreign Ministry spokesman Zhao Lijian told reporters "we are seriously prepared” if Pelosi follows through on the trip, Reuters reported. 

When pressed about what he meant, Zhao said, “If the U.S. side is bent on going its own way, China will take strong measures to resolutely respond and counteract.

"The United States should be held responsible for any serious consequences," he continued. 

In a separate article Saturday, The Financial Times reported Beijing has privately issued warnings to the U.S. that used significantly stronger rhetoric than in the past and suggested a possible military response.

Pelosi’s reported plans come amid escalating tensions between Beijing and Taiwan. 

China’s authoritarian-ruling Communist Party considers democratic, self-ruling Taiwan its own territory, to be annexed by force if necessary, and regularly advertises that threat by staging military exercises and flying warplanes into Taiwan’s air defense identification zone or across the center line of the 100-mile-wide Taiwan Strait.

Under the “One China” policy, the United States recognizes the People’s Republic of China as the sole legitimate government of China but has never accepted the Chinese Communist Party’s claim of sovereignty over Taiwan. 

Though the sides lack formal diplomatic ties, the U.S. is Taiwan’s chief provider of outside defense assistance and political support, in a reflection of its desire to limit China’s growing influence and maintain a robust American presence in the Western Pacific.

China’s tacit support for Russia’s invasion of Ukraine prompted fears that Beijing could move on Taiwan. In May, Biden said the U.S. would intervene militarily if China were to invade the island, although the White House said the comments did not signal a policy shift.

U.S. law requires Washington provide Taipei with the means to defend itself and treat all threats to the Taiwan as matters of “grave concern,” but remains ambiguous on whether it would commit forces in response to an attack from China.

On Monday, Taipei staged air raid drills and its military mobilized for routine defense exercises. While there was no direct link between China’s renewed threats surrounding Pelosi’s possible trip and Taiwan’s defensive moves, they underscore the possibility of a renewed crisis in the Taiwan Strait.

Meanwhile, Pelosi is finding rare support among Republicans. 

Sen. Ben Sasse of Nebraska said Monday, according to Politico, that the House speaker “should go to Taiwan and President Biden should make it abundantly clear to Chairman Xi (Jinping) that there’s not a damn thing the Chinese Communist Party can do about it.”

Rep. Tom Tiffany of Wisconsin tweeted that Pelosi "should ignore China's temper tantrums and proceed with her planned visit to #Taiwan. It’s time for America to stand up to the #CCP, support our friends and allies, and end the failed One China Policy.”

And Rep. Don Bacon of Nebraska wrote on Twitter: “Communist China does not get to dictate who in America can visit Taiwan.”

The Associated Press contributed to this report.