For the first time this year, the United States has sent two warships through the strategic Taiwan Strait, according to the Taiwanese government.
The move risks further heightening tensions with China, which considers Taiwan a breakaway province and has not ruled out the use of force to bring the self-ruled island under its control.
It is also likely to be viewed in Taiwan as a sign of support from US President Donald Trump's administration amid growing friction between Taipei and Beijing.
Taiwan's defence ministry said in a statement late on Thursday the US ships were moving in a northerly direction and that their voyage was in accordance with regulations.
It added that Taiwan closely monitored the operation to "ensure the security of the seas and regional stability".
There was no immediate comment from the Chinese government.
China has stepped up pressure on Taiwan since President Tsai Ing-wen, from the pro-independence ruling party, took office in 2016. It has regularly sent military aircraft and ships to circle the island on drills in the past few years.
Beijing sent several bombers and aircraft through the Bashi Channel, which separates Taiwan from the Philippines, earlier on Thursday, Taiwan's defence ministry said in a separate statement.
A similar Chinese operation was conducted on Tuesday, the ministry said, and both were monitored closely, reports aljazeera.com citing agencies.
