President Rodrigo Duterte may meet with nine world leaders on the sidelines of the ASEAN summit in Laos next week, an official said.

Foreign Affairs Assistant Secretary Hellen dela Vega of the Office of ASEAN Affairs said nine bilateral meetings are in the works but they are still subject to availability of schedules.

But it was clear that Duterte would not be meeting with United Nations Secretary General Ban Ki-moon, citing the President's "tight schedule."

READ: Duterte turns down meeting with UN chief after drug war dispute

Aside from ASEAN members, leaders of so-called ASEAN dialogue partners will also be in the summit which includes the UN.

"Kasama sila sa iba pang bansang nag-request and so naghahanap ng schedule and you know I think the President has a very tight schedule and there are very clear priorities," dela Vega said.

"Preliminary, parang malabong malabong ma-meet ni Pangulo si UN Secretary General bilaterally," she added.

Dela Vega declined to disclose for now which leaders would the President be meeting bilaterally.

The White House has earlier announced that US President Barack Obama and Duterte may have a one-on-one meeting, where the issue of human rights is expected to be raised.

"I think the President is prepared, that's why his first statement is to ask President Obama to listen to him, so he can discuss and explain to him the problem that we face as far as the drug problem is concerned so I think he's prepared for it," dela Vega said.

READ: Duterte: Obama must listen to me on human rights

Dela Vega said that while she cannot "second-guess" what the President would tell leaders in their bilateral meetings, Duterte is expected to "give insights on the thrust of his administration," discuss "overall bilateral relationships," the Philippines' upcoming chairmanship of the ASEAN, and exchange views on regional issues.

There is no information yet on whether Duterte will be meeting Chinese Premier Li Keqiang on the summit's sidelines.

"The President's press release or public messages [have been] clear, that as far as the bilateral dispute is concerned between Philippines and China, he would prefer that he discuss this bilaterally with China. But at the same time, we have to be aware of the general importance of maritime security for regional peace and stability as well," dela Vega said.

Just like the foreign ministers meeting in July, the Philippines is not expected to push for a mention of its victory in the arbitration case against China on maritime rights in the South China Sea when the ASEAN chair issues its Chairman's Statement at the end of the meet.

"No, there was no reference to arbitration. The anchor would be the joint communiqué of the ministerial meeting last July, which reflects full respect for diplomatic and legal process in paragraph 2 of the joint communiqué," dela Vega said.

Discussions on the South China Sea during the summit "might be anchored on the general situation in the South China Sea, maritime security and then the rule of law, and UNCLOS," according to dela Vega.

During the summit, the Philippines will formally accept the chairmanship of ASEAN for 2017 with the theme and logo to be unveiled. These would reflect the President's emphasis on change.