The Marines have been building their presence in Australia's North Territory since last year, Stars and Stripes reported.
The corps sent 200 to 250 personnel to Australia this summer as part of the Marine Rotational Force-Darwin.
Those Marines, as well as 750 from the 31st Marine Expeditionary Unit, are training alongside the 5th Royal Australian Regiment as part of the two-week training exercise that began Tuesday.
"Exercise Koolendong 2013 is designed as a 'proof of concept' to assess the capacity of the Bradshaw Field Training Area to accommodate live-fire training for battalion-sized units of approximately 1,000 personnel and demonstrate the capabilities that U.S. amphibious forces can provide," a statement from the Marines said.
Next year, the Marines are planning on increasing their force in Australia to 1,150 personnel, including a battalion and helicopters.
Starting in 2016, 2,500 Marines with the Air Ground Task Force will travel to Darwin on six-month rotations, Stars and Stripes said.