The US said Thursday it has launched South China Sea patrols with the Philippines and will temporarily deploy 275 troops and five warplanes in the country, escalating its presence amid a territorial dispute with China.
"In the South China Sea, China's actions in particular are causing anxiety and raising regional tensions," Defence Secretary Ashton Carter said during a visit to Manila.
The joint naval patrols, which began last month, "contribute to the safety and security of the region's waters," Carter said after meeting with Philippines President Benigno Aquino.
China claims most of the strategic and mineral-rich sea, and has built artificial islands also claimed by neighbours including the Philippines to enforce its sovereignty, while rejecting international arbitration.
The US said 275 American troops, among about 5,000 military personnel taking part in annual war games in the Philippines, are to stay behind after the exercises end on Friday.
Five A-10C Thunderbolt ground attack planes and four other aircraft will also remain until the end of the month, he said.
Some 200 are to train Filipino soldiers until the end of the month, while the remainder will be stationed at a Manila military base on an unspecified "rotational" basis to form a "command and control" unit to support increased activities between the two allies, Carter added.