The U.S. government has already informed Japan's government about the plan, the report said.

The reorganisation will be announced during the two-plus-two security meeting in Washington, D.C., on Jan. 11, the report said.

The Marines' III Expeditionary Force, comprising tens of thousands of personnel, has been based in Okinawa for decades.

(Reporting by Mariko Katsumura. Editing by Gerry Doyle)