The Philippines may ask the United States to deploy spy planes over the South China Sea to help monitor the disputed waters, President Benigno Aquino told Reuters on Monday, a move that could worsen tensions with its giant neighbour China.The two countries only recently stepped back from a months-long standoff at the Scarborough Shoal, a horseshoe shaped reef near the Philippines in waters they both claim - the latest round of naval brinkmanship over the resource-rich sea.The United States has stressed it is neutral in the long-running maritime dispute, despite offering to help boost the Philippines’ decrepit military forces. China has warned that "external forces” should not get involved."We might be requesting overflights on that,” Aquino told Reuters in an interview, referring to U.S. P3C Orion spy planes. "We don’t have aircraft with those capabilities.”There was no immediate comment from Washington.Last month, Aquino pulled out a lightly armed coast guard ship and a fisheries boat due to bad weather around the Scarborough Shoal, a group of rock formations about 140 miles (225 km) west of the main Philippine island of Luzon.