Despite rebuking accusations of attempting to militarize the South China Sea by way of their artificial island program, China responded harshly to the presence of a U.S. Navy warship traveling near to one of their claimed islands over the weekend.

The USS Stethem, an Arleigh Burke-class missile destroyer, sailed to within 12 nautical miles of Triton Island, which is part of the larger island chain known as the Paracel Islands, on Sunday in what the U.S. Navy refers to as a “freedom-of-navigation operation,” or “FONOP.”  This FONOP was intended specifically to challenge the competing claims on the island chain of three nations, Taiwan, Vietnam, and China.

Despite China claiming this area of the waterway as their own territorial waters, the United States has made it clear that they do not acknowledge Beijing’s claims of sovereignty over the Islands, and as such, will travel through it as they see fit.

“I believe the Chinese are building up combat power and positional advantage in an attempt to assert de facto sovereignty over disputed maritime features and spaces in the South China,” Adm. Harry Harris, Commander of PACOM, said on Wednesday.