Asked about the report, White House spokeswoman Sarah Sanders told a regular news briefing that the United States was "well aware of China's militarization of the South China Sea. We've raised concerns directly with the Chinese about this and there will be near-term and long-term consequences", Sanders said.
It said the YJ-12B anti-ship cruise missiles enabled China to strike vessels within 295 nautical miles.
The missiles have reportedly been deployed on Fiery Cross Reef, Subi Reef and Mischief Reef in the Spratly Islands.
Earlier media reported about the plans of China to open a new military base overseas, like "Bagnet".
The US has objected to China building the islands, and positioning defenses on them, claiming this violates worldwide law.
The US White House in a statement warned of consequences for China in view of the increasing militarisation of the South China Sea area, which is also claimed by Vietnam and the Philippines.
"We're well aware of China's militarisation of the South China Sea".
Any peaceful activities, including the deployment of necessary national defence facilities, have been created to safeguard China's sovereignty and security.
China "hopes relevant parties can objectively and calmly view this", she added. Dispute the controversy, China has been carrying land-reclamation efforts, building artificial reefs and has established air bases, radar and communication systems, naval facilities and defensive weaponry. And the HQ-9B long-range surface-to-air missiles could hit aircraft up to 160 nautical miles.
While the USA routinely conducts maritime training drills in the South China Sea, military presence in the region is regularly contested.
"China's activities in the South China Sea is to uphold our sovereignty and territorial integrity".
The same month, Australian warships en route to Vietnam were challenged by the Chinese navy as they traversed the South China Sea, leading Prime Minister Malcolm Turnbull to assert Australia's right to travel global waters.
On the topic of the South China Sea, Xi said at the time that "China does not intend to pursue militarization".
Last month, U.S. Admiral Philip Davidson, nominated to head U.S. Pacific Command, said China's "forward operating bases" in the South China Sea appeared complete.