MANILA — President Rodrigo Duterte should strive to “get the support of more countries” following his assertion of the Philippines' arbitral victory against China’s sweeping claims over contested waters, a former official said Wednesday.

Duterte, in his first speech before the United Nations General Assembly (UNGA) on Tuesday, said the Philippines "firmly rejects" any attempt to undermine the award that invalidated China's sweeping claims over the West Philippine Sea.

“The next step is for our President and his administration to put in reality the invocation of the arbitral award,” said former Foreign Affairs Secretary Albert Del Rosario.

“Our government should work earnestly to get the support of more countries so that the arbitral award will be raised more emphatically next year for the UNGA 2021,” he told ANC.

The US, the UK, Germany, France and Australia recently rejected China’s “historic claims” over nearly 90 percent of the waterway through which international trade worth trillions of dollars passes yearly.

Duterte previously shelved the arbitral award as he pursued loans and investments from Beijing. Del Rosario’s successor Foreign Affairs Secretary Teodoro Locsin also refused to raise the award before the UN.

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The President’s latest remark before the international body showed he “was not impervious, but listens to the will of his countrymen,” said Del Rosario.

“We hope that this puts to rest the misconception that bringing the arbitral award to the UNGA is re-litigating the case,” he said.

Filipinos “should now unite so that the world will help our country and force the arbitral award against China,” said Del Rosario.

“Let us not allow this opportunity to be put to waste,” he added.

The President's statement welcoming the support of other member-states is "heartening," former Supreme Court justice Antonio Carpio said in a separate statement.

"I fervently hope that this is the policy that the Duterte administration will implement across all levels – in the protection of our exclusive economic zone in the West Philippines Sea, in the negotiations for the Code of Conduct, and in gathering the support of the international community for the enforcement of the arbitral award," he said.

Carpio, Del Rosario and former Ombudsman Conchita Carpio Morales are seeking to punish Chinese President Xi Jinping over his country's destructive activities in the South China Sea, through a case before the International Criminal Court.

If the case prospers, "warrants of arrest will be issued against President Xi Jinping and others to prevent them from travelling to ICC states," said Del Rosario.

-- With a report from Jamaine Punzalan, ABS-CBN News