Japan's government has endorsed a plan for the most significant reorganisation of US troops in Japan in decades.
The redeployment of many thousands of troops is part of Washington's efforts to reorganise its military around the world to make it a more flexible force.
The plan remains a controversial issue in Japan and will be very expensive.
The deal was signed in Washington a month ago, and the detailed work on how to realise it can now get under way. The US has some 50,000 troops in Japan.
Japan has agreed to pay millions of dollars towards the cost of moving several thousand US marines off the southern island of Okinawa to the US territory of Guam.
Once the total bill for meeting all of its obligations becomes clear, it seems likely the country's defence budget will have to be cut.
Public finances here are stretched already.
There is also still much opposition on Okinawa to plans to build a new airfield there as part of the reorganisation.
The government says it will set up a body to consult with local authorities about specific projects to try to answer concerns.
Okinawa's governor has not yet given his backing to the plan. Discussions with him will continue.