The White House warned China Thursday of "consequences" for its ongoing militarization of the hotly contested waters of the South China Sea. Press secretary Sarah Huckabee Sanders issued the warning while she was responding to a question regarding CNBC's report that China had installed missile systems on outposts in the Spratly Islands, which are two-thirds of the way east from southern Vietnam to the southern Philippines. "We're well-aware of China's militarization of the South China Sea," Sanders told reporters. "There will be near-term and long-term consequences." The Pentagon also weighed in on the development. "We have been very vocal about our concerns about them militarizing these artificial islands," Defense Department spokeswoman Dana White said. "China has to realize that they have benefited from the free navigation of the sea and the U.S. Navy has been the guarantor of that."

China quietly installed anti-ship cruise missiles and surface-to-air missile systems on three of its fortified outposts in the South China Sea, a move that allows Beijing to further project its power in the hotly disputed waters, sources with direct knowledge of U.S. intelligence reports had told CNBC. Intelligence assessments say the missile platforms were deployed to Fiery Cross Reef, Subi Reef and Mischief Reef in the Spratly Islands within the past 30 days, according to the sources who spoke on the condition of anonymity. The placement of the defensive weapons also comes on the heels of China's recent South China Sea installation of military jamming equipment, which disrupts communications and radar systems. The Spratlys, to which six countries lay claim, are located approximately two-thirds of the way east from southern Vietnam to the southern Philippines.

Map of the South China Sea. CSIS Asia Maritime Transparency Initiative/CNBC