By Mark Felsenthal and Matt Spetalnick
MANILA, April 28 (Reuters) - U.S. President Barack Obama said on Monday a new military pact between the United States and the Philippines is testimony to America's "ironclad" commitment to defend the southeast Asian nation.
The U.S. president's comments came against the backdrop of tensions between the Philippines and an increasingly powerful China over remote uninhabited islands in the South China Sea.
"Our commitment to defend the Philippines is ironclad and the United States will keep that commitment because allies never stand alone," Obama said.
Sweating profusely in an unairconditioned gymnasium packed with U.S. and Filipino soldiers, veterans and their families, the president said joint U.S.-Filipino rescue efforts after November's Typhoon Yolanda were the modern-day version of the bravery shown by both country's troops during World War Two.
The military agreement between the two countries was the centrepiece of Obama's first visit to the Philippines, the United States' oldest ally in the region.
The deal, which will have an initial 10-year term, sets the framework for a beefed-up rotation of U.S. troops, ships and warplanes through the Philippines.
Obama said the accord and his visit - part of a four-nation swing through Asia - demonstrated the U.S. commitment to a "rebalancing" of resources and diplomacy towards the fast-growing region.
That commitment has been in doubt as the United States has focused on conflicts in the Middle East and Afghanistan.
"Deepening our alliance is part of our broader vision for the Asia Pacific," Obama said.
The U.S. president further stressed solidarity with the Philippines as Manila seeks international arbitration over disputed islands in a tense standoff with Beijing.
"International law must be upheld. Freedom of navigation must be preserved," Obama said. "Disputes must be resolved peacefully and not by intimidation or by force."
China claims most of the South China Sea, but the Philippines, Malaysia, Vietnam, Brunei and Taiwan also have overlapping claims to parts of those waters.
Earlier this month, a small Philippine government ship needed to evade a blockade of Chinese coastguard vessels to deliver food, water and fresh troops to a disputed shoal in the Spratly Islands.
The Philippines is seeking United Nations arbitration challenging China's "nine-dash-line" that stretches deep into the South China Sea and the maritime heart of Southeast Asia.
In the sweltering Fort Bonifacio gymnasium on Tuesday, the U.S. president peeled off his jacket and rolled up his sleeves to speak, apologising to the assembled uniform-clad troops for doing so but promising to make his remarks brief.
Afterwards, he shook hands with troops and veterans, posing for a "selfie" photo with the family of one of the Filipino veterans.
The president later toured and laid a wreath at the U.S. military cemetery in Manila, where both U.S. and Filipino soldiers are buried. The cemetery contains more than 17,000 graves of U.S. service members who died during World War Two, the largest such cemetery anywhere in the world.
Obama's visit to the Philippines was the final leg of was on the final day of a tour that also took him to Tokyo, Seoul, and Kuala Lumpur. (Additional reporting by Rosemarie Francisco; Editing by Alex Richardson)