A U.S. Navy destroyer travels within 12 nautical miles of the Spratly Islands on October 26, 2015. The Spratly islands are reefs that are submerged under high tides and only recently turned into islands through land reclamation by China. Under international law all nations can uses the seas near the reefs as opposed to rock. The U.S. wants to keep the sea lanes open for all countries. The Spratly Island reefs are located in the shipping lanes near Vietnam and Indonesia in the South China Sea, a great distance from the Chinese mainland. U.S. Secretary of Defense Ashton Carter made it his top priority when he took this position in 2015 to assert the freedom of navigation in the South China Sea. The action was taken after the Xi Jinping visit to the U.S. to tackle this issue without affecting bilateral economic and global cooperation relations with China.