The US vice president is scheduled to make a stopover on Tuesday on an island near the disputed South China Sea.
The United States is seeking an expansion of its military presence in the Philippines under a 2014 defence pact, US and Philippine officials have said.
It is one of the initiatives that will be discussed during Vice President Kamala Harris' visit aimed at countering China and rebuilding ties that were fractured over alleged human rights abuses in the Southeast Asian nation.
Harris held talks earlier on Monday with President Ferdinand Marcos Jr and other officials on the first of a two-day visit that will include a trip to western Palawan province facing the disputed South China Sea, which Beijing claims virtually in its entirety. She also held separate talks with Vice President Sara Duterte.
She also reaffirmed US commitment to defend the Philippines under the 1951 Mutual Defense Treaty in case Filipino forces, ships and aircraft come under attack in the disputed waters.
"An armed attack on the Philippines armed forces, public vessels, or aircraft in the South China Sea would invoke the US' mutual defence commitments. And that is an unwavering commitment that we have to the Philippines," Harris said.
US forces in the Philippines
The Philippines, a former American colony, used to host one of the largest US Navy and Air Force bases outside the American mainland.
The bases were shut down in the early 1990s, after the Philippine Senate rejected an extension, but American forces returned for large-scale combat exercises with Filipino troops under a 1999 Visiting Forces Agreement.
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In 2014, the longtime allies signed the Enhance Defense Cooperation Agreement, which allows larger numbers of American forces to stay in rotating batches within Philippine military camp, where they could build warehouses, living quarters, joint training facilities and store combat equipment, except nuclear arms.
After the agreement was signed, the Americans launched construction projects in five Philippine camps and areas, including in the country’s south. But many of the projects were delayed by legal issues and other problems, Philippine defence officials said.
An estimated 100 US military personnel currently remain in Zamboanga and three southern provinces, a Philippine military official told AP.
A US official told reporters new areas have been identified and would be developed to expand joint security cooperation and training.
Proposed areas for American military facilities
Philippine military chief of staff Lt Gen Bartolome Bacarro told reporters last week that the US wanted to construct military facilities in five more areas in the northern Philippines.
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Two of the new areas proposed by the Americans were in northern Cagayan province, across a strait from Taiwan that could serve as a crucial outpost in case tensions worsen between China and the self-governed island that Beijing claims as its own.
The other proposed sites included the provinces of Palawan and Zambales, he said.
They both face the South China Sea and would allow an American military presence nearer the disputed waters to support Filipino forces.
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