The U.S. government has repeatedly invoked the U.S.-Philippines mutual defense treaty regarding Chinese harassment at Scarborough Shoal and other Spratly Islands. However, the U.S. military has stopped short of providing security aid to Philippine naval and civilian vessels involved in resupplying the grounded ship at Scarborough that Manila maintains in a bid to asserts its sovereignty claims.
China has claimed some 90% of the South China Sea as its territory and the Philippines claims the Spratly Islands, where Scarborough Shoal is located, as its sovereign territory.
In August, two Chinese warplanes flew close to a Philippine Air Force turboprop plane patrolling over Scarborough Shoal and dropped flares in the flight path of the plane, putting the crew at risk, military officials said.