The US and Philippine military officials said at an opening ceremony that 3,000 Filipino soldiers and 2,500 American military personnel would take part in the annual "Balikatan," or shoulder to shoulder, exercises, the largest of several military drills the longtime allies stage each year.
American and Philippine officials said the manoeuvres would focus on maritime security and disaster response, but avoided linking the war games with their concern over China, which they have criticised for its increasingly assertive behaviour in disputed South China Sea territories.
Dozens of left-wing activists protested outside the main military camp in the Philippine capital, Manila, where the opening ceremony was held.
They said the drills and a recently signed agreement that allows a larger US military presence in the country would trample the Philippine Constitution, which prohibits foreign troops except when their presence is covered by a treaty.
Philippine Foreign Secretary Albert del Rosario said the exercises would strengthen the countries' capability to deal with increasing tensions "due to excessive and expansive maritime and territorial claims" and "aggressive patterns of behaviour" that threaten regional peace and stability.
The manoeuvre will include maritime surveillance exercises, live-fire drills, training on handling bombs and "mass casualty response," a Philippine military statement said.
