The United States has deployed at least three warships near Alaska to support homeland defense operations as China and Russia began a joint patrol in the Northern Pacific Ocean.

Photos released by the U.S. Navy show that destroyers USS Kidd and USS Sterett, as well as cruiser USS Lake Erie, conducted homeland defense operations in the Northern Pacific Ocean last month. The images did not reveal the exact location of the operations.

A U.S. Northern Command spokesperson told Newsweek that the Kidd and the Sterett were deployed to support the command’s maritime homeland defense mission. The command is charged with U.S. homeland defense, including air and sea around Alaska.

Regarding the Lake Erie‘s mission, a U.S. Pacific Fleet spokesperson told Newsweek that the U.S. Navy “frequently conducts exercises and operations in the North Pacific Ocean to maintain readiness, refine tactics, deter conflict, and support maritime homeland defense.”

Chinese and Russian warships began a series of maneuvers at the same time. A China-led exercise, the Northern/Interaction-2024, was held in the Sea of Japan and the Sea of Okhotsk, both northwest of the Pacific Ocean.

The first stage of the exercise was completed in the Sea of Japan on September 15. Later, nine Chinese and Russian warships transited off the northern coast of Japan. They headed to the Sea of Okhotsk for the second stage of the exercise, which ended on September 27.

Following the conclusion of the exercise, the Chinese and Russian warships commenced their fifth joint maritime patrol in what China’s military called “relevant waters of the Pacific Ocean.” The Russian military claimed the patrol area is in the Asia-Pacific region.

The Russian defense ministry announced on Tuesday that six warships, including four from China and two from Russia, crossed the Bussol Strait and entered the Northwestern Pacific Ocean. This naval group will conduct training and exercises during the patrol.

Bussol Strait is a waterway located in the Kuril Islands, an archipelago in the Russian Far East region that separates the Sea of Okhotsk from the Northern Pacific Ocean. It was not immediately clear whether the Chinese and Russian warships would head toward Alaska.

In August last year, a total of 11 Russian and Chinese warships approached the Aleutian Islands of Alaska during their joint patrol in the surrounding international waters. They were shadowed by four U.S. Navy destroyers and P-8 Poseidon maritime patrol aircraft.

Among the three American warships deployed in the Northern Pacific Ocean, the Kidd was the first one to be operating for homeland defense operations. The warship, which is homeported in Everett in the state of Washington, was in the area as early as September 7.

Photos released by the U.S. Navy also showed the Sterett, which is stationed at San Diego in California, was in the Northern Pacific Ocean from September 13 to 22. It had visited Dutch Harbor on Amaknak Island, part of the Aleutian Islands, during the deployment.

Meanwhile, the Lake Erie was in the same area since September 18. Photos showed the San Diego-based warship remained underway as of September 30. Both the U.S. Northern Command and the U.S. Pacific Fleet did not say when these deployments would conclude.

Besides the U.S. naval vessels, the U.S. Coast Guard has ships and aircraft operated under Operation Frontier Sentinel, an ongoing operation that is designed to “meet presence with presence” when strategic competitors, China and Russia, operate in and around U.S. waters.

The U.S. Coast Guard spotted four vessels from the Russian and Chinese counterparts near Alaska on Saturday as they transited northeastward in the Bering Sea. The Chinese Coast Guard later claimed that its ships had arrived in the Arctic Ocean for the first time ever.