The central government on Thursday gave the green light for a modified landfill plan that will see a key U.S. military base moved within Okinawa Prefecture, taking the unprecedented step of overriding the local government's objection to the plan.

The Defense Ministry will commence work to reinforce soft ground at the relocation site for U.S. Marine Corps Air Station Futenma as early as Jan. 12, a government source said.

The approval is "a milestone" for the total transfer of the Futenma air base as early as possible, Defense Minister Minoru Kihara told reporters.