The annual drills -- dubbed Balikatan, or "shoulder to shoulder" in Tagalog -- will be concentrated in the northern and western parts of the archipelago nation, near the potential flashpoints of the South China Sea and Taiwan.

China claims almost the entire waterway, a key route for international trade, and also considers self-ruled Taiwan to be part of its territory.

In response to China's growing influence, the United States has been bolstering alliances with countries in the Asia-Pacific region, including the Philippines.

Washington and Manila are treaty allies and have deepened their defence cooperation since Philippine President Ferdinand Marcos took office in 2022.

While the Philippines is poorly armed, its proximity to the South China Sea and Taiwan would make it a key partner for the United States in the event of a conflict with China.

"The purpose of armed forces, why we exist, is really to prepare for war," Philippine Colonel Michael Logico told reporters ahead of the drills.

"There's no sugarcoating it... for us not to prepare, that's a disservice to the country."

The Philippine Coast Guard will join Balikatan for the first time following several confrontations between its vessels and the China Coast Guard, which patrols reefs off the Philippines' coast.

The joint drills involve a simulation of an armed recapture of an island in Palawan province, the nearest major Philippine landmass to the hotly disputed Spratly Islands in the South China Sea.

The same exercise will be held in the northern provinces of Cagayan and Batanes, both less than 300 kilometres (180 miles) from Taiwan.

Like last year, there will be a sinking of a vessel off the northern province of Ilocos Norte.

Other training will concern information warfare, maritime security, and integrated air and missile defence.

The United States has deployed its Standard Missile-6 (SM-6) guided missiles to the Philippines for Balikatan, but Logico said the weapons would not be used in the drills.

China's foreign ministry has accused the United States of "stoking military confrontation", and warned the Philippines to "stop sliding down the wrong path".

- 'It matters for regional stability' -

The exercises, which will run until May 10, will involve around 11,000 American and 5,000 Filipino troops, as well as Australian and French military personnel.

France will also deploy a warship that will take part in a joint exercise with Philippine and US vessels.

Fourteen countries in Asia and Europe will join as observers.

For the first time, the drills will go beyond the Philippines' territorial waters, which extend about 22 kilometres from its coastline, Logico said.

"Balikatan is more than an exercise; it's a tangible demonstration of our shared commitment to each other," Lieutenant General William Jurney, commander of US Marine Corps Forces, Pacific, said in a statement.

"It matters for regional peace, it matters for regional stability."