A U.S. guided-missile destroyer sailed close to one of China’s man-made islands in the South China Sea on Tuesday, drawing an angry rebuke from Beijing, which said it had tracked and warned the ship and called in the U.S. ambassador to protest.

The USS Lassen’s patrol was the most significant U.S. challenge yet to the 12-nautical-mile territorial limits China claims around artificial islands it has built up in the Spratly archipelago as Beijing exercises its growing maritime power.

Washington’s move followed months of deliberation by the administration of President Barack Obama and could ratchet up tension in one of the world’s busiest shipping lanes and increase strains in U.S.-China relations.

A U.S. defense official said the Lassen also went within 12-mile limits of features in the disputed sea claimed by Vietnam and U.S. treaty ally, the Philippines. They said such “freedom-of-navigation” patrols were expected to become more frequent.

The U.S. destroyer sailed within 12 nautical miles of Subi Reef, an artificial island built up by China in the past year.

A Chinese guided-missile destroyer and a naval patrol ship shadowed and gave warnings to the U.S. warship “according to law”, China’s Defense Ministry said.

The U.S. patrol was a “coercive action that seeks to militarize the South China Sea region” and an “abuse” of freedom of navigation under international law, it added.

U.S. Defense Secretary Ash Carter, testifying on Tuesday to the Senate Armed Services Committee, initially would only say the U.S. Navy had conducted operations in the South China Sea. But under questioning from lawmakers, he said the USS Lassen had passed within 12 miles of a Chinese artificial island.

Read more: http://www.reuters.com/article/2015/10/27/us-southchinasea-usa-idUSKCN0SK2AC20151027