USS Lassen South China Sea China US
USS Lassen sailed within 12 nautical miles of artificial islands built by China in the South China SeaReuters

China accused the US of threatening its sovereignty and security, after a US Navy warship sailed close to artificial islands Beijing built in the South China Sea to reinforce its claim on disputed waters.

The USS Lassen deliberately passed within 12 miles of the Chinese-occupied Subi and Mischief reefs in the Spratly Islands archipelago, thus breaching into what the Beijing controversially claim as its territorial waters. The Chinese government issued an angry response expressing its "strong dissatisfaction and resolute opposition" at the manoeuvre.

"The actions of the US warship have threatened China's sovereignty and security interests, jeopardized the safety of personnel and facilities on the reefs, and damaged regional peace and stability," the foreign ministry said. "China will deal resolutely with deliberate provocations from any country," it warned.

Chinese state-run media went further. Xinhua news agency called the US manoeuvre a "highly irresponsible and dangerous" provocation. The Global Times, a Communist Party mouthpiece renowned for its nationalist rhetoric, said the military should show it is ready to fight a war over the South China Sea.

"Beijing should deal with Washington tactfully and prepare for the worst. This can convince the White House that China, despite its unwillingness, is not frightened to fight a war with the US in the region, and is determined to safeguard its national interests and dignity," the newspaper wrote.

"Beijing ought to carry out anti-harassment operations. We should first track the US warships. If they, instead of passing by, stop for further actions, it is necessary for us to launch electronic interventions, and even send out warships, lock them by fire-control radar and fly over the US vessels."

Washington said the sail-past was part of a "freedom of navigation" operation to reassert the right of free passage for vessels in what it says are international and not Chinese waters. "The whole point of freedom of navigation in international waters is that it's international waters. You don't need to consult with anybody," State Department spokesman John Kirby said.

The US claims that the 12 miles territorial boundary does not apply to the occupied reefs, as despite China's land reclamation efforts, these are not islands under international law. The UN Convention on the Law of the Sea, states that islands are only "naturally formed" areas of land. Partially submerged reefs expanded with man-made structures should thus not qualify.

The Spratly Islands area is a resource-rich archipelago of reefs and atolls west of the Philippines, parts of which are claimed by Manila, Vietnam, Malaysia, Brunei and Taiwan.