Australia and the United States have begun their biggest-ever joint military exercises, aimed at sending a message both to allies and potential foes, including China.
Tension over China's more assertive activity, particularly in the disputed South China Sea, has raised fears of confrontation.
The exercises involve 33,000 U-S and Australian troops on board battleships equipped with strike jets.
Head of the U-S Pacific Command, Admiral Harry Harris, said the size of the deployment was intended as a signal.
