China’s military said  it was monitoring U.S. Navy vessels sailing through the Taiwan Strait, maintaining a high alert and ready to defeat any provocations.

The U.S. Navy said the guided-missile cruisers USS Antietam and USS Chancellorsville conducted a “routine Taiwan Strait transit” on Sunday, in accordance with international law.

The United States has no formal diplomatic relations with Taiwan but is bound by law to provide the island with the means to defend itself.

China has never ruled out using force to bring Taiwan under its control.

Taiwan says the People’s Republic of China has never ruled the island and so has no claim to it, and that only Taiwan’s 23 million people can decide their future.