China said it warned and tracked a U.S

China said it warned and tracked a U.S. Navy warship as it came close to one of its artificial islands in the South China Sea’s contested waters

Cui Tiankai, Chinese ambassador to the United States, told CNN’s Christiane Amanpour on Tuesday that the U.S. operation is "a very serious provocation, politically and militarily."

Cui said it was a clear attempt by Washington to militarize the region

"It is a very absurd and even hypocritical position to ask others not to militarize the region while one’s self is sending military vessels there so frequently," he said

The Ministry of Foreign Affairs said that the vessel "illegally entered into the waters of China’s Spratly Islands."

"The action taken by the U.S. warship has threatened China’s sovereignty and security interest, and has put the safety of personnel on the reefs in danger," a ministry statement said

Two Chinese warships and naval warplanes monitored and warned the American vessel, the Defense Ministry said

A U.S. defense official told CNN that the destroyer USS Lassen "conducted a transit" within 12 nautical miles of Subi Reef in the Spratly Islands on Tuesday morning

The operation put the ship within an area that would be considered Chinese sovereign territory if the United States recognized the man-made islands as being Chinese territory, the official said

The United States hadn’t breached the 12-mile limit since China began massive dredging operations to turn three reefs into artificial islands in 2014 -- even though maritime law doesn’t usually accord territorial waters to islands built on previously submerged reefs

U.S. Defense Secretary Ash Carter, testifying before a Senate panel, said the missions will continue

"We will fly, sail and operate wherever international law permits and whenever our operational needs require," he said