Two US Navy warships sailed through international waters in the Taiwan Strait on Sunday, the first such operation since US House Speaker Nancy Pelosi’s visit to Taiwan angered China, which claims the island as its territory. The US Navy, confirming a Reuters report, said the cruisers Chancellorsville and Antietam were conducting the ongoing operation. Such operations typically take eight to 12 hours to complete and are closely monitored by China’s military. In recent years, US warships, and occasionally those from allied nations such as Britain and Canada, have regularly sailed through the straits, angering China, which claims Taiwan over the objections of its democratically elected government. Pelosi’s trip to Taiwan in early August angered China, which saw it as an attempt by the US to interfere in its internal affairs. China then began military exercises near the island, which have continued ever since. “These (US) ships crossed a corridor in the straits that is beyond the territorial waters of any coastal state,” the US navy said. The operation demonstrates the United States’ commitment to a free and open Indo-Pacific, and the US military flies, sails and operates wherever international law allows, the Navy said. John Kirby, a spokesman for the US National Security Council, echoed that position on CNN, saying the passage of the ships was “very consistent” with the US’s “one China” policy and the pursuit of a “free and open Indo-Pacific”. . Kirby added that the operation had been planned for a long time. The Chinese military’s Eastern Theater Command said it was monitoring the ships and warning them. “Troops in theater remain on high alert and are ready to prevent any provocation at any time,” he added in a statement. Taiwan’s defense ministry said the ships were sailing south and that its forces were monitoring, but that “the situation was normal”. The narrow Taiwan 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 to Taiwan was followed about a week later by a group of five other US lawmakers, with China’s military responding by conducting more exercises near the island. Sen. Marsha Blackburn, a U.S. lawmaker on the Senate Commerce and Armed Services committees, arrived in Taiwan on Thursday for the third visit by a U.S. official this month, defying pressure from China to freeze travel. US President Joe Biden’s administration has sought to keep tensions between Washington and Beijing from escalating into conflict, reiterating that congressional travel is routine. The United States 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 says the People’s Republic of China never ruled the island and so has no claim to it, and that only Taiwan’s 23 million people can decide their future. Our Morning Update and Afternoon Update newsletters are written by Globe editors, giving you a concise summary of the day’s most important headlines. Sign up today.