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MANILA — A political analyst on Monday urged President Ferdinand Marcos Jr.'s to assert the landmark 2016 arbitration ruling that invalidated China's expansive claims in the South China Sea during the 77th United Nations General Assembly.

his will be Marcos' "chance" to bring up the country's legal victory against Beijing before world leaders in New York, according to De La Salle University international studies professor Renato De Castro.

"This will be the first time for our President, a sitting President, to articulate our victory in the arbitral ruling, in a person-to-person context in the United Nations General Assembly, something that has not been done before," he told ANC"s "Headstart".

In 2020, former President Rodrigo Duterte affirmed the Permanent Court of Arbitration’s ruling before UNGA in a pre-recorded speech.

Marcos is set to speak at the UN high-level meeting on Tuesday, Sept. 20, where he is expected to discuss issues on food security, agriculture, renewable energy, and climate change.

In his departure speech on Sunday, Marcos said the Philippines would affirm also its "commitment to the ideals of the UN, citing its contributions to peaceful settlement of disputes and of international law and the highlighting the importance of the UN in fostering international dialogue and cooperation".

• Marcos Jr. leaves for US to attend United Nations general assembly

It will be his first engagement with the International body, and his first visit to the US after being elected as chief executive.

De Castro said Marcos' participation in UNGA is "in a way" representing Southeast Asia.

"Given the US-China strategic competition in the region and ASEAN's effort to emphasize its centrality, President Bongbong Marcos is talking in a way not simply as a Filipino President but as one of the leaders, in fact a new leader in Southeast Asia," he said.

The Permanent Court of Arbitration in The Hague upheld in 2016 the Philippines’ rights to its 200-nautical-mile exclusive economic zone, rejecting China’s historic claim to resources in the South China Sea using its 9-dash line doctrine.

China claims large parts of the South China Sea and is ramping up its militarization activities in the resource-rich waters. Other claimants, such as Malaysia, Taiwan and Vietnam, contest the territorial claims.