MANILA - President Rodrigo Duterte may have raised the Philippines' arbitral victory against China before the UN General Assembly as most of Beijing's promises remain unfulfilled despite Manila's "friendliness," a maritime expert said Thursday.

Duterte, in his first speech before the UN assembly, said the Philippines "firmly rejects" any attempt to undermine the award that invalidated China's sweeping claims over the West Philippine Sea.

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Beijing's continued and increased aggression in the disputed South China Sea in the past year may also be why the President raised the award before the international community, said Prof. Jay Batongbacal, director of the University of the Philippines Institute for Maritime Affairs and Law of the Sea.

"Despite his friendliness and accommodation to China, he (Duterte) has not really gotten much. All the promises of infrastructure, development aid and financing still have not borne much fruit compared to the promises so there’s a lot of disappointment there," he told ANC.

"Second, the concern that especially in the past year China has been increasingly assertive in the South China Sea to the point they’re really imposing themselves in surrounding countries like Vietnam and Malaysia, carrying out seismic explorations in their waters."

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The Philippines only avoided this due to its supposed joint development with China which has since been in deadlock, Batongbacal added.

He also cited the statement of Foreign Affairs Secretary Teodoro Locsin Jr. that Manila suspended its abrogation of its Visiting Forces Agreement with the US as China asserted itself in the disputed waters during the COVID-19 pandemic.

"It probably took 4 years for the patience to run out or for the realization to set in that they're not getting anything from China. They only have about 2 years left in their term, and 1 year will be preoccupied with the elections," Batongbacal said.

The Philippines has many "legal options" and and can use many "international conventions" to call China to account over its destruction in the West Philippine Sea, according to Batongbacal.

"There may not be necessary a litigation but definitely they are still useful for generating international and political pressure to get China to actually stop this kind of behavior," he said.

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Batongbacal had earlier said that China will not act on a pending communication before the International Criminal Court in an "official or formal level" but may somewhat change its behavior.

"That’s against their interest also especially this Chinese dream of national rejuvenation where they see themselves as becoming a world leader by 2050. Even if they ignore this, I think they will somehow alter their behavior in order to avoid further accusations of being a rogue state and seen as an untrusty member of the international community," he said.