The South China Sea is a major strategic waterway for trade and oil shipments to Japan, Korea as well as southern China. It has been the focus of a maritime dispute which has continued now for over six decades, with competing claims from China, Vietnam, the Philippines, Indonesia and Brunei. Recently China has become more assertive in pressing its claims – harassing Vietnamese fishing vessels and seizing reefs in the Philippine claim zone. China has insisted that it has ''indisputable sovereignty'' over the area and has threatened to enforce its claim.