United States President Joe Biden said Washington's defense commitment to Manila is "ironclad" following collisions between Chinese and Philippine vessels in the West Philippines last Sunday.

In a joint press conference with Australian Prime Minister Anthony Albanese on Wednesday (US time), Biden asserted Washington's readiness to invoke its Mutual Defense Treaty with the Philippines in the face of the People's Republic of China's increasing aggression in the WPS.

"Just this past week, PRC vessels acted dangerously and unlawfully as our Philippine friends conducted a routine resupply mission within their own exclusive economic zone in the South China Sea," he said.

"I want to be clear — I want to be very clear: The United States' defense commitment to the Philippines is ironclad. The United States' defense agreement with the Philippines is ironclad," Biden stressed.

Citing Article IV of the MDT, the US President warned that "any attack on Filipino aircraft, vessels, or armed forces will invoke" America's defense pact with the Philippines.

Probe ordered

Under the MDT signed in 1951, the United States and the Philippines agreed that an armed attack in the Pacific on either of the parties would be dangerous to the peace and safety. They would act to meet the common danger per their respective constitutional processes.

Biden made the remarks after the National Task Force for the West Philippine Sea on Sunday accused the CCG of performing "dangerous blocking maneuvers" that resulted in a collision with the Unaiza May 2, an indigenous boat contracted by the Armed Forces of the Philippines for its routine resupply mission to the BRP Sierra Madre.

The NTF-WPS condemned the "provocative, irresponsible, and illegal action" of the CCG, which it said "imperiled the safety" of the Unaiza May 2 crew. A second boat, the Unaiza May 1, was able to complete the resupply mission. 

During the same mission, a Chinese maritime militia vessel "bumped" into the Philippine Coast Guard BRP Cabra's port side while escorting the resupply boats. The incident happened approximately 6.4 nautical miles northeast of Ayungin Shoal.

President Ferdinand Marcos Jr. ordered the Philippine Coast Guard to investigate the collisions between the Philippine and Chinese boats — the closest encounter in weeks.

Earlier this week, US National Security Advisor Jake Sullivan assured Philippine National Security Advisor Eduardo Año of US support in safeguarding its sovereign rights in the WPS under the two nations' MDT.

Condemnation

In a separate statement, Biden and Albanese stressed the importance for all states to "exercise rights and freedoms in a manner consistent with international law as reflected in the United Nations Convention on the Law of the Sea, including freedom of navigation and overflight."

The two leaders also expressed their "strong opposition" to China's "destabilizing actions" in the South China Sea, including the "unsafe encounters at sea and in the air, the militarization of disputed features, and the dangerous use of coast guard vessels and maritime militia."

The American and Australian leaders also condemned China's efforts to interfere with the "routine Philippine maritime operations around Second Thomas Shoal, and efforts to disrupt other countries' offshore resource exploitation."