The Unites States has said it would welcome a move by Japan to extend air patrols into the South China Sea amid rising tensions over China's territorial claims in the region.
Japanese aircraft patrol parts of the East China Sea, where Tokyo and Beijing have clashed over the sovereignty of an island chain. If Japan were to expand its programme of surveillance flights to cover the South China Sea it could lead to further antipathy between the region's biggest economies.
Japan does not have territorial interests in the South China Sea, but its mineral rich waters have led to a series of clashes over islands and the potential to extract resources. Beijing claims almost all of the sea for itself, overlapping with claims from Vietnam, Malaysia, the Philippines and Taiwan.
"I think allies, partners and friends in the region will look to the Japanese more and more as a stabilising function," a senior US navy officer told Reuters news agency.
"In the South China Sea, frankly, the Chinese fishing fleet, the Chinese coast guard and the (navy) overmatch their neighbours," said Admiral Robert Thomas.
Japan's prime minister Shinzo Abe has pushed for a stronger military role for his country in the region.
US support for an extension of Japan's role comes as the two allies negotiate bilateral security guidelines for the region, part of president Barack Obama's pivot to Asia.