A spokeswoman for the foreign ministry said on Monday that China more forcefully warned the United States about U.S. Speaker of the House Nancy Pelosi’s possible trip to Taiwan, according to the Financial Times.

The Financial Times story, released on Saturday, quoted six people acquainted with the Chinese warnings and stated that they were much more severe than previous threats issued by Beijing in response to the United States’ treatment of Taiwan, which it claims as its own.

At a routine press briefing on Monday, spokeswoman Zhao Lijian responded to questions regarding the report’s details by saying, “We are seriously prepared.”

When asked what China was “seriously prepared for,” whether military or diplomatic, 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 added.

The State Department and the White House National Security Council declined to comment on the Times article. The Times claims Pelosi intends to visit Taiwan in August.

China has increased its military presence in the region of Taiwan to exert pressure on the democratically elected administration there to recognize Chinese sovereignty. Taiwan’s government asserts that only the 23 million residents of the island can decide its destiny and that, despite its desire for peace, it will defend itself if attacked.

President of the United States Joe Biden announced on Wednesday that he intends to talk with Chinese President Xi Jinping by the end of the month. Biden seemed to question Pelosi’s alleged travel to Taiwan.

“I think that the military thinks it’s not a good idea right now, but I don’t know what the status of it is,” Biden said.

Monday saw air raid drills in Taipei, Taiwan’s capital, and military mobilization for regular defense drills amid worries of a retaliatory Chinese response to Pelosi’s potential visit.

Although there was no apparent connection between China’s latest threats and Taiwan’s defensive actions, they highlight the likelihood of a new crisis in the Taiwan Strait, which is thought to be a possible flashpoint for conflict that might involve the whole region.

The military was conducting its annual multi-day air and sea exercises and the deployment of tanks and personnel while air raid sirens were sounding throughout Taipei.

U.S. Gen. Mark Milley, the top U.S. military official, claimed that the Chinese military has grown much more aggressive and dangerous over the last five years. He made his remarks during a tour to the Indo-Pacific that included a stop Sunday in Indonesia.

The number of Chinese ships and planes intercepting the U.S. and other ally troops in the Pacific region has increased noticeably throughout that time, according to Milley, the chairman of the Joint Chiefs of Staff, and the number of dangerous engagements has increased proportionately as well.

“The message is the Chinese military, in the air and at sea, have become significantly more and noticeably more aggressive in this particular region,” said Milley, who recently instructed his team to gather information on relations between China, the United States, and other countries in the area.

Public opinion in the U.S. is shifting toward Taiwan. More than half of Americans favor protecting Taiwan in the case of an invasion, and 69% support official recognition, according to a survey conducted last year by the Chicago Council on Global Affairs.