It’s the third time this year American vessels entered the strait in a move certain to stoke tensions with China.

The United States sent two Navy ships through the Taiwan Strait, the third such operation this year as the US military increases operations in the strategic waterway despite opposition from China.

The voyage on Wednesday will add to tensions with China, but is likely to be viewed in self-ruled Taiwan as a sign of support from US President Donald Trump’s government amid growing friction between Taipei and Beijing.

“The ships’ transit through the Taiwan Strait demonstrates the US commitment to a free and open Indo-Pacific,” the US Pacific Fleet said in a statement. “The US Navy will continue to fly, sail and operate anywhere international law allows.”

An anonymous US official told AFP news agency that Chinese ships asserted a “presence” during Wednesday’s sailing, but all interactions between the two navies were “safe and professional”.

Taiwan’s defence ministry said the island’s forces monitored the two ships in the strait and it was a normal transit through international waters.

There was no immediate reaction from China. Beijing protested after the US Navy sailed two warships through the Taiwan Strait on October 22, characterising the move as an affront to its sovereignty.

US-China flashpoints

The latest move comes ahead of an expected meeting between Trump and Chinese President Xi Jinping in Argentina on the sidelines of a G20 summit.

The US Navy conducted a similar mission in the strait’s international waters in July, the first in about a year.

Washington has no formal ties with Taiwan, which China claims as a “breakaway province”, but is bound by law to help the island defend itself and is its main source of arms.

The Pentagon says Washington has sold Taiwan weapons valued at more than $15bn since 2010.

China has been ramping up pressure to assert its sovereignty over the island.

Over the weekend, Taiwan’s ruling pro-independence Democratic Progressive Party suffered heavy losses in mayoral and county elections to the China-friendly Kuomintang, which has been welcomed by Beijing.

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