The US Navy sailed two warships through the Taiwan Strait yesterday, in the first such transit publicised since US House Speaker Nancy Pelosi visited Taiwan earlier in August, at a time when tensions have kept the waterway particularly busy.

The USS Antietam and USS Chancellorsville are conducting a routine transit, the US 7th Fleet said. The cruisers "transited through a corridor in the strait that is beyond the territorial sea of any coastal state," the statement said.

China conducted many military exercises in the strait as it sought to punish Taiwan after Pelosi visited the self-ruled island against Beijing's threats.

China has sent many warships sailing in the Taiwan Strait and waters surrounding Taiwan since Pelosi's visit, as well as sending warplanes and firing long-range missiles. It views the island as part of its national territory and opposes any visits by foreign governments as recognising Taiwan as its own state.

China said it tracked the movement of the ships. "Troops of the (Eastern) Theatre Command are on high alert and ready to foil any provocation at any time," said senior Colonel Shi Yi, spokesperson for the People Liberation Army's Eastern Theater Command.

The US Navy is sailing the USS Chancellorsville and the USS Antietam warships through the Taiwan Strait. Photo / AP

White House National Security Council spokesman John Kirby, speaking on CNN, said the transit sent a "very clear message, very consistent message ... that the United States Navy, the United States military will sail, fly and operate wherever international law permits us to do so."

Kirby also noted the transit was "very consistent with our 'One China' policy, very consistent with our desire to make sure that we can continue to work toward a free and open Indo-Pacific."

The US regularly sends its ships through the Taiwan Strait as part of what it calls freedom of navigation manoeuvres.

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The 100 mile-wide (160-kilometre-wide) strait divides Taiwan from China.

- AP