Japan wants to give planes to the Philippines that Manila could use for patrols in the South China Sea, sources said, a move that would deepen Tokyo's security ties with the Southeast Asian nation most at odds with Beijing over the disputed waterway.

Four sources with knowledge of the matter told Reuters that Japan was looking to offer three Beechcraft TC-90 King Air planes that could be fitted with basic surface and air surveillance radar.

They said talks within the Japanese government were preliminary and would need to overcome legal hurdles. Japan had yet to formally propose the planes as an alternative to more sophisticated Lockheed Martin P3-C aircraft that Manila wants to track Chinese submarine activity, they added.