The top Democrat and Republican on the Senate Armed Services Committee are voicing concern over an agreement with Japan on the reorganisation of US forces based on the southern island of Okinawa.
Chair Carl Levin, ranking Republican John McCain and Democrat Jim Webb have told Defense Secretary Leon Panetta that no agreement should be considered final without congressional approval.
The US and Japan agreed in February to proceed with plans, previously criticised by the senators as too costly, that would transfer thousands of US troops from Okinawa, sending some to Guam.
Panetta discussed the issue by phone with his Japanese counterpart Monday, and a Pentagon statement said the specifics of the plan would be announced in the very near future.
Japanese prime minister Noda is visiting Washington next week.