TAIPEI (REUTERS) - A United States warship sailed through the sensitive Taiwan Strait on Saturday (Feb 26), part of what the US military calls routine activity, which nonetheless irritates China.

The US Navy's 7th Fleet said the Arleigh Burke-class guided-missile destroyer USS Ralph Johnson was conducting a "routine" transit through international waters.

"The ship's transit through the Taiwan Strait demonstrates the United States' commitment to a free and open Indo-Pacific," 7th Fleet spokesman Nicholas Lingo said in a statement. "The United States military flies, sails, and operates anywhere international law allows."

Taiwan’s Defence Ministry said the ship sailed in a northerly direction through the Strait, that its forces had monitored its passage and observed nothing out of the ordinary.

Taiwan is currently in a heightened state of alert due to Russia’s invasion of Ukraine, nervous that China may try to take advantage of the situation to make a move on the island though the government has reported no unusual Chinese manoeuvres.

Last year, US naval ships transited the Strait roughly monthly. Saturday's sailing was the first since November.

China regards Taiwan as a renegade province awaiting reunification with the mainland, by force if necessary.

Beijing has mounted repeated air force missions into Taiwan's air defence identification zone (ADIZ) over the past two years, provoking anger in Taipei.

Beijing calls Taiwan the most sensitive and important issue in its relations with Washington.

Like most countries, the US has no formal diplomatic ties with Taiwan but is its most important international backer and arms supplier.