Three top U.S. lawmakers are expressing concern about an agreement on the re-organization of U.S. forces on the Japanese island of Okinawa, which they say is imminent.

The lawmakers say in a formal statement that Washington and Tokyo are expected to announce the deal Wednesday, but Japanese media say the announcement has been postponed.

The two countries hope to finalize a long-delayed plan to relocate a strategic American military base to a less crowded part of Okinawa because of local complaints about noise, pollution and crime.

But in their statement Tuesday, U.S. Senators Jim Webb, John McCain and Carl Levin say no deal should be considered final until it has the support of the U.S. Congress. They say they are worried about the costs and strategic implications of the plan.

Japan's Kyodo news agency reports Wednesday that the announcement has been postponed in response to the statement by the U.S. lawmakers, all of whom belong to the Senate Armed Services Committee.

But the report quotes a top government official saying details of the deal will likely be released before Japanese Prime Minister Yoshihiko Noda begins a visit to Washington on Monday.

Japan's Mainichi newspaper says a delegation of Japanese politicians discussed the relocation scheme with a group of U.S. senators in Washington Tuesday. It does not say whether these are the same senators who issued the statement.

Other Japanese press reports say the agreement calls for the United States to gradually transfer several military bases on Okinawa back to Japanese control.

In February, Washington and Tokyo agreed to go ahead with the transfer of 8,000 troops from Okinawa to the U.S. territory of Guam. But a final decision was not reached on closing the Futenma air base, also on Okinawa.

A joint statement at the time said both countries remain fully committed to replacing the Futenma facility and the relocation of its air base to Camp Schwab, which is also on Okinawa. Futenma is located in a congested urban area of Okinawa and is unpopular with residents because of the added stress it puts on local infrastructure.

But plans to build a replacement base for the Marines in a less congested coastal area have met with strong resistance from environmentalists and other groups.

The U.S. has some 47,000 troops in Japan, mostly on Okinawa.