The Philippines is seeking a "stronger commitment" from the United States to help its ally, the defense minister said on Monday, as China asserts its sovereignty over disputed areas of the South China Sea.

China claims most of the South China Sea, through which $5 trillion in ship-borne trade passes every year, and the Philippines, Vietnam, Malaysia, Taiwan and Brunei have overlapping claims.

China said on Monday it had lodged a complaint with the United States over a U.S. spy plane that flew over parts of the disputed South China Sea in a diplomatic row that has fueled tension between the world's two largest economies.

Philippine Defense Minister Voltaire Gazmin said he would meet U.S. Defense Secretary Ash Carter on Wednesday in Hawaii to ask for a stronger commitment.

"I will ask about the extent of the assistance they will give us, what they can do to help us because right now we are being oppressed," Gazmin told journalists at a naval base south of Manila.

"We feel concerned about what is happening in the West Philippine Sea (South China Sea). Freedom of navigation, freedom of flight is disrupted so that even U.S. aircraft flying at the international territory are challenged."

A senior military official told Reuters Gazmin would ask Washington to provide second-hand planes, ships and coastal radar systems.

Next week, Gazmin will join President Benigno Aquino on a three-day visit to Tokyo to discuss the rising tension in the South China Sea.

He said the two sides would also discuss the transfer of Japanese military equipment to the Philippines to boost maritime security.

(Reporting by Manuel Mogato; Editing by Nick Macfie)