The Philippines needs up to four squadrons (48) of upgraded Lockheed Martin F-16 fighter jets, more well-armed frigates and corvette-size, fast to surface combatant vessels and minesweepers and four to six mini submarines, possibly obtained from Russia, to build a credible defense force in the face of China’s increasing belligerence in the South China Sea, the Center for a New American Security (CNAS) said.