A US official told CNN that the guided missile destroyer USS Higgins and the cruiser USS Antietam sailed with 12 miles from four of the Paracel Islands, which the US Navy calls a "navigational freedom", meaning enforcement of the law for free access in international waters.
China has in recent years reinforced many of the islands in the South China Sea military facilities and advanced others through land reclamation.
Beijing says that a large part of the South China Sea is its territory, claims the majority of the international community as spurious.
Vietnam, the Philippines, Taiwan, Indonesia, Malaysia and Brunei also claim parts of the South China Sea.
An international court ruled in 201
Washington is taking freedom in navigation to enforce the right of free passage in contested waters.