MANILA - Former officials who filed a complaint against Chinese President Xi Jinping before the International Criminal Court did what his Filipino counterpart, President Rodrigo Duterte, was "unwilling and unable to undertake" for Philippine sovereignty, Sen. Risa Hontiveros said Sunday.

Xi and other Chinese officials allegedly committed crimes against humanity in implementing Beijing's "systematic plan to control the South China Sea," Filipino fishermen, former Foreign Affairs Secretary Albert del Rosario and former Ombudsman Conchita Carpio-Morales said in their complaint.

Hontiveros, in a statement, thanked Del Rosario and Carpio-Morales "for accomplishing what President Rodrigo Duterte is unwilling and unable to undertake: his job to safeguard and protect Philippine sovereignty and us Filipinos against China."

The complainants, she said, "provided us with a powerful template of courage as we continue to assert our sovereignty in the West Philippine Sea."

"They clearly underscored the difference that can be made by standing up against foreign aggression instead of pursuing President Duterte's hollow and treacherous foreign policy," she added.

The opposition lawmaker also said Carpio-Morales' role in the complaint "signifies, once more, women's strong and progressive leadership and proves that a woman of principles can do the job a toxic macho can't."

It was during Del Rosario's time as top Philippine diplomat that the country brought China before a UN-backed arbitral tribunal in 2013 for incursions in the country's exclusive economic zone within the disputed South China Sea.

The tribunal, based in The Hague, invalidated China's 9-dash line claim over the waters and recognized traditional fishing rights of Filipinos in the Scarborough Shoal, an area where Beijing's patrol ships had shooed away Philippine fishermen.

The Philippines and China have long sparred over the South China Sea, but relations improved considerably under President Rodrigo Duterte, who set aside the 2016 landmark legal victory for enhanced ties.

Manila quit the world's only permanent war crimes tribunal after the ICC launched in 2018 a preliminary examination of Duterte's drug crackdown that has killed thousands and drawn international censure.

The Philippine defection from the court took effect last March 17.

ICC Prosecutor Fatou Bensouda the following day said her examination into the allegations against Duterte would continue.

The ICC, however, is unlikely to investigate Xi given Manila's departure from the court, and the complaint's citing of crimes against the environment instead of crimes against humanity, said David Bosco, an associate professor at Indiana University's School of Global and International Studies.

The complaint may also be "a futile exercise" because the ICC "has no jurisdiction over China," Duterte's spokesperson Salvador Panelo was quoted as saying on Saturday.

With a report from Agence France-Presse