U.S. Marine Brig. Gen. Craig Timberlake said the exercise at a sprawling Philippine naval reserve in the coastal town of San Antonio in Zambales province would allow the military allies to operate jointly in a range of scenarios, including responding to disasters.

He refused to discuss whether or not the annual drill, which has been staged for 28 years, was now being held partly to address concerns by Asian countries like the Philippines over China’s growing naval power. China has expressed unhappiness in the past over such drills near disputed South China Sea regions.

The Oct. 17-28 military maneuvers involve about 2,000 Marines and 1,000 Filipino counterparts. Both sides have said the exercises were not aimed at China or any country as an imaginary target.

"The long-term objective is to have better inter-operability between the two militaries," Timberlake told The Associated Press, adding the marines have also engaged in disaster relief work and humanitarian missions.

"If you can do those things, then you can branch out and do other things that brings us together," he said.

Under a brutal sun, nine amphibious vessels darted ashore and unloaded American and Filipino marines, who laid on the beach’s scorching sand to assess, their assault rifles pointed inland.

They then dashed toward a hill in batches, their movement coordinated through two-way radios and hand signs, then engaged mock enemies in a battle while about 300 Filipino navy students watched from a distance.

Marine Col. Andrew MacMannis said it was an opportunity for the Americans to show their Filipino counterparts advanced U.S. equipment and learn combat skills from each other.

A Filipino participant, 1st Lt. Erwin Borja, said amphibious assaults were also taught in the local marines corps. "The difference is in the equipment, we don’t have AAVs," Borja said, referring to the U.S. amphibious assault vehicles used in the mock assault.

The 120,000-strong Philippine military is among Asia’s weakest. The Philippines, a U.S. defense treaty partner, is relying on Washington to help modernize its aging naval fleet, which includes many World War II vessels, one of which is among the oldest active warships in the world.

Philippine officials have said the government is also looking at buying more ships, helicopters, jet trainers and air defense radars to better patrol its territorial waters and safeguard its claims over the potentially oil-rich Spratly Islands in the South China Sea which are also being claimed by China and four other countries.

The Philippine and Vietnam, which is also a Spratlys claimant, have repeatedly accused Chinese vessels this year of interfering with their oil and gas explorations and harassing fishermen within their 200 nautical mile exclusive economic zones.

Beijing has named the South China Sea one of its "core interests," meaning it could potentially go to war to protect it. Washington angered Beijing last year when it declared the peaceful resolution of the disputes and the freedom of navigation in the vast ocean, home to some of the world’s busiest sea lanes, were in the U.S. national interest.

Scarborough shoal, which is disputed by China and the Philippines, lies off Zambales, the venue of Sunday’s exercises. An Oct. 27 drill will involve a mock raid by about 100 U.S. and Filipino marines from an American warship to capture a hostile beachhead in western Palawan province, which faces the Spratly Islands.

One Filipino-occupied Spratly island was proposed as a possible site for the current joint training but was ruled out to avoid antagonizing China and other claimants. The island lies close to a Spratly reef occupied by Chinese forces and an island separately occupied by Vietnamese forces. The information came from two Filipino officials who spoke on condition of anonymity because they were not authorized to talk to reporters.