US officials revealed that two US Navy warships crossed international waters in the Taiwan Strait, in the first operation of its kind since US House Speaker Nancy Pelosi's visit to Taiwan.
And Reuters news agency quoted 3 US officials - who spoke to the agency on condition of anonymity - that the US Navy cruisers "Chancellorsville" and "Antietam" are carrying out the crossing, which is still underway, according to Reuters.
These operations usually take between 8 and 12 hours to complete and are closely monitored by the Chinese military.
In recent years, American warships, and sometimes ships from allied countries such as Britain and Canada, have begun to sail through the strait permanently, which angers Beijing.
China - which considers Taiwan part of its territory - began military exercises near the island after Pelosi's visit in early August, and those exercises are still continuing.
Pelosi's visit angered Beijing, which viewed it as an American attempt to interfere in China's internal affairs.
Other visits
About a week after Pelosi's visit, a group of five other US lawmakers visited Taiwan, and the Chinese military responded by conducting more exercises near the island.
Senator Marsha Blackburn, a member of the Senate Commerce and Armed Services Committees, arrived in Taiwan on Thursday for the third high-profile US visit this month, defying pressure from Beijing to halt such visits.
The Taiwan Strait has been a constant source of military tension since the then-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.
Taiwan's government says that the People's Republic of China has never ruled the island and therefore has no claim to it, and that only its 23 million people can decide their future.