The Philippines "must be dissuaded from making any further provocation in the South China Sea, or otherwise China will not sit by idly", a former senior Chinese leader warned on Tuesday.

Former State Councilor Dai Bingguo made the remark at a dialogue on the South China Sea between Chinese and US think tanks in Washington.

He said that although China possesses the ability to recover the islands that were illegally occupied by other countries, "in the interest of regional peace and stability, China has all along exercised enormous restraint".

The dialogue was held as the Arbitral Tribunal in The Hague, established at Manila's unilateral request despite China's objection, was scheduled to announce its ruling on the South China Sea arbitration case on July 12. US, a major ally of Manila, has publicly pressed Beijing to accept the ruling.

The former top Chinese diplomat said the South China Sea might sink into chaos, and so might all of Asia, if the momentum of provocation in the region goes unchecked.

Dai also said China would not be intimidated by US actions, "not even if the US sent 10 aircraft carriers to the South China Sea".

"To be blunt, when the US states today that it does not take a position on issues of territory, it actually amounts to backpedaling and defiance of the postwar international order, which the US itself participated in building."

He said the Xisha Islands and Nansha Islands, illegally occupied by Japan during World War II, were restored to China after the war in accordance with the Cairo Declaration and the Potsdam Proclamation.

"Many of you were probably not aware of this, but China's actions to restore the islands were supported by General Douglas McArthur," Dai said.

Shi Yinhong, an expert on US studies with Renmin University of China, said if there are provocations from either the Philippines or the US and others after the ruling, "China will certainly respond, in both diplomatic and military ways".

Myron Nordquist, associate director and editor of the Center for Oceans Law and Policy at the University of Virginia School of Law, said he believes the US is behind the issue "because it wants to get back to the military base it was kicked out of".