The commander of the U.S. Pacific Fleet has joined a surveillance mission over the South China Sea as part of a visit to the Philippines.
The Navy released photos Sunday of Admiral Scott Swift on board a P-8A Poseidon aircraft during a seven hour surveillance mission that took place on Saturday. It is not known what areas of the sea were covered by the mission.
U.S. surveillance flights in the area have been a source of annoyance for China, which claims almost the entire sea and has maritime territorial disputes with several countries, including the Philippines and Vietnam.
The United States, which says it does not take sides in the territorial disputes, has increased its maritime security cooperation with Hanoi and Manila in recent years. Washington has said freedom of navigation in the region must be preserved and disputes be resolved peacefully.