The U.S. Navy sent a guided-missile destroyer within 12 nautical miles of artificial islands built by China in the South China Sea on Tuesday, a U.S. defense official said, in a challenge to China's territorial claims in the area.
The official said the USS Lassen was sailing near Subi and Mischief reefs in the Spratly archipelago, features that were submerged at high tide before China began a massive dredging project to turn them into islands in 2014.
"The operation has begun ... It will be complete within a few hours," said the official, who spoke on condition of anonymity.
The mission would be the start of a series of challenges to China's territorial claims in one of the world's busiest sea lanes, another U.S. defense official said.
The second official earlier said the ship would likely be accompanied by a U.S. Navy P-8A surveillance plane and possibly P-3 surveillance plane, which have been conducting regular surveillance missions in the region.
The patrols represent the most serious U.S. challenge yet to 12-nautical-mile territorial limits China claims around the islands and are certain to anger Beijing, which said last month it would "never allow any country" to violate its territorial waters and airspace in the Spratlys.
China's Foreign Minister Wang Yi said Beijing was trying to verify if the U.S. ship had entered the 12-mile zone.
"If true, we advise the U.S. to think again and before acting, not act blindly or make trouble out of nothing," the Foreign Ministry quoted Wang as saying.
The Chinese Embassy in Washington said the concept of freedom of navigation should not be used as an excuse for muscle flexing and the United States should "refrain from saying or doing anything provocative and act responsibly in maintaining regional peace and stability."
Additional patrols would follow in the coming weeks and could also be conducted around features that Vietnam and the Philippines have built up in the Spratlys, the second U.S. official said.
"This is something that will be a regular occurrence, not a one-off event," said the official. "It's not something that's unique to China.