MANILA, Philippines: During a visit to the Philippines, U.S. Vice President Kamala Harris will demonstrate America's commitment to defending its treaties by flying to an island province facing the disputed South China Sea, where Washington has accused China of bullying smaller nations.

This week, she met with President Ferdinand Marcos Jr. for talks aimed at reinforcing Washington's oldest treaty alliance in Asia and strengthening economic ties.

Later in the week she will fly to Palawan province, where she will be the highest-ranking U.S. leader to visit the frontier island at the forefront of the long-seething territorial disputes involving China, the Philippines, Vietnam, Malaysia, Brunei and Taiwan.

Coast guard spokesperson Commodore Armand Balilo said the Philippine coast guard is scheduled to welcome Harris on board one of its largest patrol ships, the BRP Teresa Magbanua, in Palawan, where she will deliver a speech.

Meanwhile, Philippine Ambassador to Washington Jose Manuel Romualdez said Harris' trip to Palawan shows the level of America's support to an ally and concern over China's actions in the disputed sea.

"That is as obvious as you can get, that the message they're trying to impart to the Chinese, is that 'we support our allies like the Philippines on these disputed islands,'" Romualdez told The Associated Press.

Washington and Beijing have long been on a collision course in the contested waters.

Over the weekend Harris spoke briefly with Chinese leader Xi Jinping while heading into a closed-door meeting at APEC. When asked on whether they discussed Taiwan or North Korea, she responded that they talked about "keeping open lines of communication."

Harris also plans to meet Vice President Sara Duterte, daughter of Marcos' predecessor Rodrigo Duterte, who has defended her father's deadly "War on Drugs" that left thousands of suspects dead and sparked an International Criminal Court investigation as a potential crime against humanity.

After her meeting with Marcos Jr., Harris plans to meet civil society activists to highlight the commitment and continued support pf the U.S. for human rights and democracy.