MANILA, Philippines — The United States today revealed for the first time that American ships have started conducting joint patrols with the Philippines in the South China Sea, a somewhat rare move not done with many other partners in the region.

At the same time, Defense Secretary Ash Carter announced at a joint news conference with Philippine Defense Secretary Voltaire Gazmi that the United States will be keeping nearly 300 troops, including Air Force commandos armed with combat aircraft and helicopters, in the Philippines through the end of the month. It’s part of a military build-up sure to inflame tensions with Beijing in the South China Sea.

The U.S. will also begin sending forces on increased rotations into the Philippines, it was disclosed, to beef up training and to support increased military operations in the region.

Speaking in the guest house of the presidential complex, Carter said the U.S. military moves are not meant to provoke anyone, but instead said “we’re trying to tamp down tensions here..”

But Gazmin said he expects that the U.S. forces, “with their presence here, will deter uncalled-for actions by the Chinese.”