By Paul Eckert
WASHINGTON (Reuters) - Three influential Senators on Tuesday questioned an expected new U.S.-Japan agreement on relocating American military bases from Okinawa, raising concerns about costs and strategy of the latest effort to resolve a festering bilateral dispute.
Senators Carl Levin, John McCain and Jim Webb - all members of the Senate Armed Services Committee - told Defense Secretary Leon Panetta that "no new basing proposal can be considered final until it has the support of Congress."
The lawmakers' letter to Panetta said they expected Washington and Tokyo to unveil as early as Wednesday the latest revision of a much-delayed 2006 plan to move 8,000 Marines from Japan's southern island of Okinawa to the U.S. territory of Guam to address Okinawan complaints about noise, pollution and crime.
"We have serious questions that have not been fully addressed regarding the emerging agreement between the administration and the Government of Japan," the senators said in a statement accompanying the letter.
"These questions pertain to the core details of this or any basing arrangement, including cost estimates, military sustainment and force management, and how it would support a broader strategic concept of operations in this increasingly vital region," they said.
The latest turn in the Okinawa issue - a point of friction since the 1995 gang rape of a schoolgirl by U.S. servicemen sparked outrage against American bases - comes days before Japanese Prime Minister Yoshihiko Noda is to visit Washington.
There are a total of about 47,000 U.S. troops in Japan under a 1960 bilateral security treaty. Okinawa, occupied by the United States from 1945-72, accounts for less than 1 percent of Japan's total land, but hosts three-quarters of U.S. military facilities in the country in terms of land area.
According to an outline of the agreement reported by Japan's Yomiuri Shimbun newspaper, the United States will hand back to Japan five bases and facilities in Okinawa in three stages, integrating them with other existing U.S. bases on the island.
Japan would also help finance plans to upgrade U.S. military facilities on Tinian and Pagan in the Northern Mariana Islands, and the two allies would hold joint military exercises on those U.S.-controlled islands, the daily newspaper said.
The Senators told Panetta in the letter they were "fully committed to a robust U.S. presence in the Asia-Pacific region" and viewed the U.S.-Japan alliance as the "cornerstone" of U.S. policy in the region.
But they said they sought more details on how the plan fit into the Obama administration strategy of "rebalancing" U.S. forces to focus on the Asia-Pacific region, a leading center of world trade and home to nuclear saber-rattling North Korea and a rapid military build-up by China.
"We also remain concerned about the absence of firm cost estimates informed by basing plans, an analysis of logistical requirements, and environmental studies related to this new agreement," the senators' letter said.
(Reporting By Paul Eckert; Editing by Sandra Maler)