The Philippines has begun separate naval exercises with the United States and Japan on an island province facing the disputed South China Sea, displaying its security alliances amid an increasingly tense territorial rift with Beijing.

Philippine military officials, however, stressed Monday that the weeklong exercises are aimed at enhancing disaster-response readiness and are not directed at any country or linked to the dispute.

U.S. Navy Rear Adm. William Merz said at the opening of the U.S.-Philippine exercises on Palawan island that Washington's alliance with countries like the Philippines allows American forces to operate "where it matters, when it matters."

Filipino sailors will hold a separate search and rescue drill on Wednesday with Japan's Maritime Self Defense Force, which deployed a P-3 Orion surveillance plane to Palawan over the weekend.