The guided-missile cruisers USS Antietam and USS Chancellorsville were conducting a “routine transit through the Taiwan Strait,” the US 7th Fleet said in a statement. “The passage of ships through the Taiwan Strait demonstrates the United States’ commitment to a free and open Indo-Pacific,” it said. “The United States military flies, sails, and operates wherever international law allows.” US warships, and sometimes ships from allied nations such as Britain and Canada, have crossed the strait in recent years, angering Beijing. China’s military said on Sunday it was monitoring US ships sailing through the Taiwan Strait, maintaining high alert and ready to defeat any challenge. China, which claims Taiwan as its own territory, began military exercises near the island after Pelosi’s visit in early August, and those exercises have continued. Her trip angered Beijing, which saw it as an attempt by the US to interfere in China’s internal affairs. US Navy operations in the Taiwan Strait typically take eight to 12 hours to complete and are closely monitored by the Chinese military. The strait has been a frequent source of military tension since the defeated government of the Republic of China fled to Taiwan in 1949 after losing a civil war with the Communists, who founded the People’s Republic of China. Pelosi’s visit was followed about a week later by a group of five other US lawmakers, with China’s military responding by conducting more exercises near Taiwan. Sen. Marsha Blackburn, who sits on the Senate Commerce and Armed Services committees, arrived in Taiwan on Thursday for the third visit by a US official this month, defying pressure from Beijing to freeze the trips. The Biden administration has sought to keep tensions between Washington and Beijing from escalating into conflict, reiterating that such congressional trips are routine. The US does not have formal diplomatic relations with Taiwan, but is bound by law to provide the island with the means to defend itself. China has never ruled out using force to bring Taiwan under its control. Taiwan’s government says the People’s Republic of China has never ruled the island and therefore has no right to claim it, and that only its 23 million people can decide their future. Reuters contributed to this report