Multiple Chinese warships shadowed the two US vessels during the transit in a move certain to anger Beijing.

Two American warships sailed through the Taiwan Strait in a move bound to aggravate China amid heightened tensions with Beijing.

The USS Curtis Wilbur and USS Antietam conducted a routine transit on Monday to demonstrate US commitment “to a free and open Indo-Pacific”, Commander Nate Christensen, deputy spokesman for US Pacific Fleet, said in a statement.

“The US Navy will continue to fly, sail and operate anywhere international law allows,” he said.

Multiple Chinese warships shadowed the two US vessels during the transit, following at a safe distance. There was no immediate comment from China.

The voyage risks further heightening tensions with China, but will likely be viewed in self-ruled Taiwan as a sign of support by President Donald Trump‘s government, amid growing friction between Taipei and Beijing.

It was the second time in three months US warships have conducted so-called “freedom of navigation” exercises in the 180km-wide stretch of water.

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Taiwan’s defence ministry confirmed the transit saying “US ships routinely passed the international waters of the Taiwan Strait”.

‘Independence forces’

China sees Taiwan as part of its territory to be reunified, despite the two sides being ruled separately since the end of a civil war on the mainland in 1949.

Beijing recently conducted a series of military manoeuvres, including a live fire exercise in the Taiwan Strait in April, declaring its willingness to confront Taiwan’s “independence forces”.

Washington remains Taipei’s most powerful unofficial ally and its main arms supplier despite switching diplomatic recognition to Beijing in 1979.

The Pentagon says Washington has sold Taiwan more than $15bn in weaponry since 2010.

The Trump administration has sought closer ties to the island, announcing plans last month to sell it $330m in spare parts for several aircraft including the F-16 fighter and the C-130 cargo plane.

Taiwan’s premier William Lai said during a parliamentary session on Tuesday that Taiwan respected the US’s right of passage in international waters and recognised “the various efforts of the US in maintaining peace in the Asia-Pacific region”.

Taiwan’s defence ministry said in an earlier statement the military was “closely monitoring the US warships during their passage”.

Taiwan is only one of a growing number of flashpoints in the US-China relationship, which also include a bitter trade war, American sanctions, and China’s increasingly muscular military posture in the South China Sea.