A U.S. Navy warship sailed within 12 nautical miles of an artificial island built up by China in the South China Sea, U.S. officials said on Wednesday.

It was the first such challenge to Beijing in the strategic waterway since U.S. President Donald Trump took office.

The officials, speaking on condition of anonymity, said the USS Dewey traveled close to the Mischief Reef in the Spratly Islands, among a string of islets, reefs and shoals over which China has territorial disputes with its neighbors.

The so-called freedom of navigation operation, which is sure to anger China, comes as Trump is seeking Beijing’s cooperation to rein in ally North Korea’s nuclear and missile programs.

Territorial waters are generally defined by U.N. convention as extending at most 12 nautical miles from a state’s coastline.

One U.S. official said it was the first operation near a land feature which was included in a ruling last year against China by an international arbitration court in The Hague. The court invalidated China’s claim to sovereignty over large swathes of the South China Sea.

The U.S. patrol, the first of its kind since October, marked the latest attempt to counter what Washington sees as Beijing’s efforts to limit freedom of navigation in the strategic waters.

The United States has criticized China’s construction of the man-made islands and build-up of military facilities in the sea, and expressed concern they could be used to restrict free movement.

U.S. allies and partners in the region had grown anxious as the new administration held off on carrying out South China Sea operations during its first few months in office.