A United States nuclear-powered aircraft carrier conducted a war game with ally the Philippines in the contested South China Sea last week while China carried out “combat-readiness” patrols.

Newsweek has reached out to the U.S. Seventh Fleet, the Armed Forces of the Philippines and the Chinese Defense Ministry for comment by email.

Why It Matters

USS Carl Vinson has been operating in the South China Sea since late December last year. It is deployed with F-35C stealth aircraft, the U.S. Navy‘s most capable fighter jet.

China‘s claims in the South China Sea cover nearly all maritime features but overlap with those of neighboring countries, including the Philippines, and have often led to clashes at sea. Manila is an ally of Washington as both sides maintain a mutual defense treaty.

What To Know

The U.S. Seventh Fleet said the Carl Vinson Carrier Strike Group, which also included a cruiser and two destroyers, as well as a P-8A maritime patrol aircraft, concluded a two-day Maritime Cooperative Activity, or MCA, with the Philippine armed forces on Saturday.

This fifth iteration of the MCA reinforced maritime cooperation and coordination, the Philippine military said, which has mobilized two ships and two fighter aircraft for communication and maneuver exercises, as well as aircraft combat training.

The MCA highlighted a longstanding partnership with its Philippine counterpart in the maritime domain, the U.S. Seventh Fleet said, showcasing a “collective commitment” to strengthening cooperation in support of a free and open Indo-Pacific region.

According to the Philippine military, the MCA was carried out near Palawan, which is the country’s westernmost province in waters in the South China Sea that fall within Manila’s 200-nautical-mile exclusive economic zone.

While the U.S. and the Philippine militaries were conducting exercises in the South China Sea, the Chinese military patrolled an undisclosed location in the region with maritime and air units, the People’s Liberation Army Southern Theater Command said in a statement.

The patrols were aimed at maintaining regional peace and stability, according to the Southern Theater Command, whose area of responsibility covers the South China Sea.

“Any military activities that disrupt the South China Sea are under control,” it said.

What People Are Saying

U.S. Navy Rear Admiral Michael Wosje, commander of the Carl Vinson Carrier Strike Group, said: “The U.S. and the Philippines are ironclad allies. As fellow maritime nations, we share the common goal of a free and open Indo-Pacific, assuring access to the seas.”

Philippine General Romeo Brawner Jr., the Armed Forces of the Philippines Chief of Staff, said: “This MCA is a crucial element of our continued efforts to strengthen defense cooperation. With each exercise, we become increasingly prepared and effective in addressing the challenges ahead.”

What Happens Next

The U.S. is likely to conduct another MCA with the Philippines this year. It remains to be seen whether Manila will hold similar activities with U.S. allies like Japan and Australia.