MANILA - The United States on Sunday proposed several measures to deepen its defense cooperation with the Philippines following China's recent aggression in the West Philippine Sea.

US Secretary of Defense Lloyd Austin III said he spoke with his Filipino counterpart Delfin Lorenzana by phone to reaffirm their "shared commitment to the US-Philippines alliance."

"I had a productive call with SND (Secretary of National Defense) @del_lorenzana to discuss challenges in the South China Sea and the need for unity in ensuring security and stability in the region," he said in a tweet.

I had a productive call with SND @del_lorenzana to discuss challenges in the South China Sea and the need for unity in ensuring security and stability in the region. #FreeandopenIndoPacific

— Secretary of Defense Lloyd J. Austin III (@SecDef) April 11, 2021

Austin also reiterated the US' commitment to "maintaining a free and open Indo-Pacific, rooted in international law, including the UN Convention on the Law of the Sea," according to a statement from his office.

"The two leaders also affirmed the value of the US-Philippines Visiting Forces Agreement. They pledged to stay in close contact," the statement read.

The Philippines and the United States have a mutual defense treaty signed in 1951.

In a separate statement, the Philippines' Department of National Defense (DND) confirmed the two officials' discussion on "the situation in the West Philippine Sea and recent developments in regional security."

The West Philippine Sea refers to the maritime areas on the western side of the Philippine archipelago, including the Luzon Sea as well as the waters around, within and adjacent to the Kalayaan Island Group and Bajo De Masinloc, also known as Scarborough Shoal.

China claims almost the entire South China Sea, and disregards an international arbitration ruling in 2016 that invalidated such claim.

Austin and Lorenzana "are looking forward to the conduct of Exercise Balikatan, which was cancelled last year", as the former "reiterated the importance of the VFA," the DND said.

President Rodrigo Duterte ordered last year the abrogation of the VFA, which governs the conduct of visiting American troops, after the US visa of his close ally, Senator Ronald "Bato" dela Rosa, was cancelled.

But it had been twice suspended amid the COVID-19 pandemic and other developments in the region.

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Austin "hopes that (the VFA) would be continued" and Lorenzana "committed to discuss the matter" with Duterte, the DND statement read.

The officials' telephone conference comes after Chinese ships chased off a Filipino boat carrying fishermen and an ABS-CBN News crew in the West Philippine Sea on April 8.

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Lorenzana earlier demanded the withdrawal of Chinese ships at the Julian Felipe Reef in the West Philippine Sea, which were first sighted on March 7.

The Department of Foreign Affairs last week filed another diplomatic protest against China, vowing to do so every day until all Chinese ships have left the reef.

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Malacañang, which has pursued friendlier ties with China in exchange for investments and infrastructure funding, was mum on the boat chase and deferred to the foreign affairs and defense departments.

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China has been ramping up militarization and island-building activities in the resource-rich waterway.

Meanwhile, Lorenzana asked for Austin's assistance for the prompt delivery of the COVID-19 vaccine developed by Moderna that the Philippines has ordered, the DND said.

The US official said he would look into it and bring up the matter with the relevant office, said the DND.

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