This year, Beijing has been demonstrating its assertiveness over the energy-rich waters, prompting the US to denounce its "bullying behaviour" there and step up its own freedom of navigation operations.
In July, Mike Pompeo, the US secretary of state, declared that Washington will consider Beijing's pursuit of resources in the South China Sea as illegal. Experts say the increased military presence from both sides has raised the risk of a clash, intentional or accidental.
On Saturday, the US Navy broke its own record for the number of times it has sent a warship through the Taiwan Strait in a single year, with the guided-missile destroyer USS Mustin making the 13th transit through the 110-wide waterway that separates China from Taiwan.
The Chinese Communist Party claims to own Taiwan even though it has never ruled there and has threatened to invade if the island refuses to be peacefully annexed. The US has strong informal ties with Taiwan's democratically elected government and is its biggest arms supplier.
Meanwhile, the USS John S McCain last week was practising anti-submarine warfare with France's nuclear-powered submarine FS Emeraude and Japan's helicopter destroyer JS Hyuga in the Philippine Sea.
In a statement about its Spratlys voyage, the US Navy said China's "unlawful and sweeping maritime claims" posed "a serious threat to the freedom of the seas, including the freedoms of navigation and overflight, free trade and unimpeded commerce" for other nations in the region.
An estimated US$5 trillion ($7t) of international trade passes through the South China Sea every year, adding to concerns about China's control over its waters and raising the possibility that it could use its access as a means of economic coercion.
Beijing is also keen to tap into the huge oil and gas reserves that are believed to lie beneath its seabed.
Earlier this year it earned a stinging rebuke from Vietnam over its suspected oil surveys in the area and by creating two administrative units on the Paracel and Spratly Islands.
China has denied any wrongdoing. In its warning today, the PLA accused the US of undermining the peace and stability of the region.
"Such actions by the US have seriously violated China's sovereignty and security and severely undermined peace and stability in the South China Sea," Tian said.
