The United States just upped its game in the contested South China Sea by sending an aircraft carrier strike group — with the Pearl Harbor destroyer USS Chung-Hoon along — into waters that China claims as its own.

The Navy said today the John C. Stennis strike group “is conducting routine operations in the South China Sea. The ships transited the Luzon Strait March 1 and have maintained a location in the eastern half of these international waters for four days.”

Stennis, Chung-Hoon, the destroyer USS Stockdale and cruiser Mobile Bay conducted a replenishment at sea today receiving advanced biofuel, aviation fuel and supplies from the USNS Rainier.

The Navy said flight operations have occurred daily with Carrier Airwing 9 conducting 266 sorties.

“Numerous” People’s Liberation Army Navy vessels have remained in the carrier strike group’s vicinity, the Navy said.

“We have Chinese ships around us that we normally didn’t see in my past experience,” said Capt. Greg Huffman, Stennis’ commanding officer. “Everything I have heard over bridge-to-bridge channels has been good communications between professional mariners.”

In recent months, other ships have conducted similar events in the region, including by the destroyers USS Curtis Wilbur, USS Lassen, USS Preble and USS McCampbell, as well as the amphibious assault ship USS Essex, the amphibious dock landing ship USS Ashland, the cruiser USS Chancellorsville, and the littoral combat ship USS Fort Worth, the Navy said.

China has demanded that other nations respect its sovereignty claims to large areas of the South China Sea, which the United States rejects.

The United States wants other nations to also conduct freedom of navigation exercises in the waters it believes are international.

Adm. Harry B. Harris Jr., head of U.S. Pacific Command, recently noted on a trip to India that “some countries seek to bully smaller nations through intimidation and coercion,” without mentioning China by name.

Islands and reefs in the South China Sea are claimed by a handful of countries. China has added surface-to-air missiles, radars, deep water ports and airfields in the Spratly and Paracel islands, raising tensions.

The Stennis strike group is the centerpiece of the Great Green Fleet, a yearlong initiative highlighting the Navy’s efforts to transform its energy use to increase operational capability. The strike group is using energy efficiency measures, to include technologies and operational procedures, and alternative fuel in the course of its normal operations, the Navy said.

The Chung-Hoon left Pearl Harbor in late January with a crew of more than 300.

“Departing on deployment is a significant event in the life of all sailors.” Cmdr. Tom M. Ogden, commanding officer of Chung-Hoon, said at the time. “Months of training, maintenance, and preparations all make a ship ready for deployed operations. The crew has succeeded at every task leading up to this and deployment will be the capstone of those tremendous efforts.”

Helicopter Maritime Strike Squadron 37 Detachment 7, homeported at Marine Corps Base Hawaii, was scheduled to embark Chung-Hoon for the deployment. Detachment 7, known as “Paniolo,” was scheduled to deploy with a total of 28 personnel and two MH-60R Seahawk helicopters, the U.S. Navy’s primary anti-submarine and anti-surface warfare platform.