Philippine President Rodrigo Duterte has said he will not raise the South China Sea issue during an Asean summit in Laos next month, but disputes over these waters will have to figure in planned bilateral talks between Manila and Beijing.

"I will only bring up the issue when we are together face to face," Mr Duterte said at a news conference.

"If you quarrel with them now and you claim sovereignty, make noise here and there, they might not even want to talk. What if they tell us they don't want to talk? Can we do anything?" he said.

"We can't. We declare war? It's not an option... I would not be stupid to do that," he added.

Asean leaders are set to meet in Laos from Sept 6 to 8.

As in recent meetings, the group is unlikely to issue a statement on the South China Sea that could provoke China.

In a joint communique issued at the end of their meeting in Laos last month, Asean's foreign ministers omitted mention of an international tribunal's ruling on July 12 striking down China's claims to nearly all of the South China Sea.

TALK FACE TO FACE I will only bring up the issue when we are together face to face. If you quarrel with them now and you claim sovereignty, make noise here and there, they might not even want to talk. PHILIPPINE PRESIDENT RODRIGO DUTERTE, referring to the South China Sea issue and China.

Philippine Foreign Minister Perfecto Yasay said he "vigorously" pushed for the inclusion of the ruling in the communique.

But he had to concede that it is a matter between the Philippines and China alone, and does not involve the rest of Asean.

Manila has instead been moving to open bilateral talks with Beijing.

Former interior minister Rafael Alunan, who accompanied former president Fidel Ramos to Hong Kong last week to meet with Chinese officials, said the two sides discussed a "two-track" approach to dealing with the issue and the tribunal's ruling.

He said official talks can focus on non-contentious issues, such as letting Filipinos fish near a disputed shoal and joint exploration for oil and gas, while "encouraging track two or think-tank exchanges... where we will be discussing contentious issues".

"That would relieve us of the burden of discussing contentious issues because we have another group doing that, while we explore ways and means on how to move our relations forward," he told reporters.

But he did not say which think-tanks would be involved.

Asserting Mr Duterte's position, the government's top lawyer, Mr Jose Calida, said the Philippines will not concede any of its gains from the ruling.

"The baseline for the negotiations will be the decision. The negotiations must respect the decision," said Mr Calida, the Solicitor-General.

Political analyst Richard Heydarian of De La Salle University in Manila said that while bilateral talks show promise, Mr Duterte has to be careful.

"It is a temporary tactical shift that is justifiable, but no guarantee of bearing any strategic fruits. China has a long record of duplicity and foot-dragging while building facts on the ground. So there is a risk that Beijing will take Mr Duterte for a ride," he said.