Japan and the United States are reported to have reached a broad agreement to transfer 4,700 US marines from Okinawa to Guam.
Washington originally planned to move eight thousand marines and their dependants to the territory under a deal reached with Tokyo in 2006.
Japanese newspapers are reporting remaining troops will go to Hawaii and the Philippines instead of Guam.
China's growing military activity and US budgetary constraints are factors reported to be behind the proposal to disperse the marines over a wider area.
Guam's Governor Eddie Calvo has described the planned military build-up as a way out of poverty for thousands of people in Guam.
An official announcement is expected on Monday.