(UPDATE) PRESIDENT Ferdinand Marcos Jr. on Wednesday warned that the potential for outright conflict between the Philippines and China over their territorial dispute in the South China Sea "is much higher now than it was before."

"We worry in the Philippines because it could come from, not a strategic decision by anyone saying, 'OK, we're going to war,' but just by some servicemen making a mistake, or some action that's misunderstood," the President said in an interview with Australian journalist Sarah Ferguson on the sidelines of the Asean-Australia Special Summit in Melbourne. "That's why the ongoing attempt is always to try and lower the temperature down [when] the rhetoric is up."

Marcos said he viewed the recent actions by China against Philippine vessels "with great alarm," but this was not enough to invoke the Mutual Defense Treaty (MDT) with the US.

"I do not think that it is a time or the reason to invoke the Mutual Defense Treaty. However, we continue to view with great alarm these continuing dangerous maneuvers and dangerous actions that are being done against our seamen, our coast guard," Marcos told reporters before flying back to Manila.

"They damaged the cargo ship and caused some injury to some of our seamen, and I think that we cannot view this in any way but in the most serious way. We will make our objections known and hope that we can continue to communicate to find a way so that such actions are no longer seen in the West Philippine Sea," he added.

The Chief Executive noted that one way both countries can peacefully address the territorial dispute is by establishing a direct line between Manila and Beijing where he and Xi can discuss issues at the highest level.

"In fact, in January of last year, when I went to Beijing and I visited with President Xi Jinping, that is what I proposed. A kind of hotline between us, so that if there is a message that needs to be sent from one president to another, we can be assured that that message will reach them," he said.

Asked if he has established that direct line with the Chinese leader more than a year since his last visit to China, Marcos said, "Not yet, I'm afraid."

Marcos reiterated that the Philippine government, under his watch, will not cease in defending the country's sovereignty.

"Our sovereignty is sacred. We will not compromise it in any way. We are a sovereign nation. We will not allow a single square millimeter of our maritime rights to be trampled upon. The Philippines now finds itself on the frontline against actions that undermine regional peace, erode regional stability and threaten regional success," he said.

"We don't see it as countering the military power of any country whatsoever. It's merely the defense of our territory. We have territorial conflicts with other countries, Malaysia, for example, and Vietnam, but we've come to an arrangement with them to resolve any such conflicts peacefully," he added.

Speaking at the leaders' plenary session of the Association of Southeast Asian Nations (Asean)-Australia Special Summit, Marcos urged Australia to continue its engagement to ensure peace and stability in the Indo-Pacific region.

He acknowledged Australia's consistent support for all Asean-led mechanisms, which he said is evident in the 50 years of its dialogue partnership with the region.

"We appreciate the evolution of Australia's strategic approach towards the region from the mere confines of the Asia-Pacific to our now wider common interests in the Indo-Pacific," Marcos told Australia and the Asean leaders.

"We thus encourage Australia to continue its active engagement both bilaterally and through Asean to ensure the primacy of peace and stability through confidence building, preventive diplomacy, and conflict resolution in the region," he added.

The President also thanked Australia for its consistent support for the rule of law, the 1982 United Nations Convention on the Law of the Sea (Unclos), as well as the 2016 Arbitral Award that invalidated China's massive claims in the South China Sea.

Australia, along with the United States and Japan, earlier voiced their opposition to China's latest aggressive actions against Philippine vessels conducting routine resupply operations for Filipino troops in the Ayungin Shoal off the West Philippine Sea.

The President urged the Asean, Australia and all like-minded states to exercise boldness in maintaining respect for the rules-based international order in the face of aggressive maneuvers by Chinese vessels in the West Philippine Sea.

Marcos said that it remains the responsibility of each state to promote and protect the rule of international law "as much as any other state facing wanton military might."

He noted that the "ominous" geopolitical developments in Ukraine, the Middle East, the Korean Peninsula, and the South China Sea, among others, "pose serious challenges to the capacity of our global and regional security architecture to manage and resolve tensions, and to protect the principles of sovereignty, sovereign rights, and territorial integrity."

"A rules-based international order emanates from the lessons of history. Conflicts and war necessitated an international order based on institutions and rules which are of universal import. We need not repeat history in order to recognize its lessons," Marcos said.

"Let me be clear: We encourage our Asean neighbors to frame conflicts not simply as rivalry between major powers but as direct challenges to the sovereignty of independent states whose well-being, both politically and economically, are interdependent and intertwined," he added.

Marcos emphasized that "peace is both a global public good and one of humanity's highest values that no one state should put at risk, for whatever gain or motive."

Meanwhile, former Chief Justice Antonio Carpio said the Philippines should shift its activities in Ayungin (Second Thomas) Shoal from military to civilian so it can lodge complaints against the harassment by China before the United Nations.

For example, he said, the government should put up a civilian lighthouse and a marine research center at the shoal.

"Currently, the [resupply] missions are military, and we cannot go to the Unclos to complain. If we shift the activity to a civilian activity and China stops the resupply, then we can go to the tribunal again," Carpio said at the Kapihan sa Manila Hotel.

He added that the lighthouse and the maritime research center should be operated by the Philippine Coast Guard (PCG), a civilian organization.

Rotation and resupply (RoRe) missions are a routine task to sustain military forces deployed in the West Philippine Sea and maintain a Philippine presence in its exclusive economic zone.

But Carpio said the Armed Forces of the Philippines' (AFP) efforts to resupply the BRP Sierra Madre constitutes a military activity that is outside the scope of the United Nations Convention on the Law of the Sea (Unclos) and compulsory arbitration, based on the arbitral award of July 12, 2016.

The Philippines has filed over 200 diplomatic complaints since 2017, following the continuous harassment by the Chinese in Ayungin Shoal.

The AFP reported that the China Coast Guard and Chinese maritime militia vessels have harassed, blocked, deployed water cannons and executed dangerous maneuvers in an attempt to stop the resupply missions.

"The dangerous maneuvers conducted by China Coast Guard and maritime militia vessels violate the International rules on the Safety of Life at Sea. That's very clear. But the problem is, where do we go to complain?" Carpio said.

He suggested the government deploy more Coast Guard vessels to accompany and protect the resupply ships or to conduct international joint patrols with the United States and other states if China does not stop blocking the Philippine vessels.

He said the US or other countries that join the Philippines in joint patrols will not violate any laws as Ayungin Shoal is part of the country's exclusive economic zone.

The pro-Beijing think tank Asian Century Philippines Strategic Studies Institute led by Herman Tiu Laurel said Carpio's comments at the Kapihan sa Manila Bay "proves once and for all that Malacañang, the Department of Defense, Department of Foreign Affairs and the PCG are all wrong in saying their basis for the RoRe missions to Ayungin Shoal is Unclos."

In other developments, a US maritime expert said nearly a dozen ships belonging to China's People's Armed Forces Maritime Militia have returned to Escoda (Sabina) Shoal in the West Philippine Sea, which is within the Philippines' exclusive economic zone.

Retired US Air Force Col. Ray Powell, director of SeaLight, a maritime transparency project that monitors and reports activities in the South China Sea, said they were able to identify at least 21 PAFMM vessels that are "rafted" together at Escoda Shoal, which falls under the jurisdiction of Kalayaan in Palawan.

Sen. Francis Tolentino said the Philippines has the right to declare its rights and entitlements over maritime zones, including the underwater features, after Chinese Foreign Ministry spokesman Mao Ning said that by passing the proposed Philippine Maritime Zone Law, the Senate of the Philippines has "attempted to further enforce the illegal arbitral award on the South China Sea by domestic legislation."

WITH JAVIER JOE ISMAEL AND CLAIRE BERNADETTE MONDARES