The first of 1,200 American troops have arrived at the former US base at Subic Bay in the Philippines for joint military exercises.
Some 450 soldiers arrived at the base, near the capital, Manila, for operation Balikatan, which means shoulder-to-shoulder.
The aim is to rehearse measures to deal with security and terrorist threats, and will also involve 2,500 FiIippino troops.
The exercise is separate from joint manoeuvres to be held later this year on Sulu island against suspected Muslim rebels, in which the Americans will play a supporting and advisory role.
From the newsroom of the BBC World Service