Philippine President Rodrigo Duterte has warned Beijing to back off from a disputed island in the South China Sea, warning of possible military action if China "touches" it amid rising tensions over the key waterway.Duterte, aiming to attract trade and investment from the Asian superpower, has mostly withheld his early criticism of Beijing's expansive claims to the sea – a point of regional contention because trillions of dollars of goods pass through it.But as the Philippine m