Cost of F-22 fighter for Japan as much as $250 mln

* Sources describe Sen. Inouye letter to Japan ambassador

* US Air Force said more supportive of possible exports

WASHINGTON, June 5 (Reuters) - The U.S. Air Force estimates it would cost Japan as much as $250 million per plane to buy dozens of radar-evading F-22 fighter jets, a U.S. senator told Japan’s ambassador in a letter, saying he hopes to reverse a current U.S. ban on such exports.

Senator Daniel Inouye, who heads the Senate Appropriations Committee, said this price included the cost of creating an export version of the most advanced U.S. fighter, built by Lockheed Martin Corp LMT.N. This assumes production would begin in four to five years, with deliveries in seven to nine years, according to two sources familiar with the letter.

Rob Blumenthal, a spokesman for Inouye, confirmed the senator had sent letters on the F-22 issue to the ambassador, Ichiro Fujisaki, and to Defense Secretary Robert Gates. He declined to release the letters or discuss their content.

The sources, who asked not to be named since the issue is still far from decided, said the U.S. Air Force had reversed its opposition to F-22 exports after studying the issue of F-22 exports again over the past four to six months.

The estimated cost is far higher than the roughly $150 million paid by the Air Force for its last batch of fighters, but the price tag would come down considerably if Congress decides to add funding for more U.S. F-22s to the fiscal 2010 budget, the sources said.

“That would help quite a bit because it would avert the cost of restarting the production line once it had stopped,” said one of the sources.

Gates in April said the Pentagon would halt production of the F-22 fighter at 187 airplanes, after ordering four more in fiscal 2009 that ends Sept. 30.

Top Air Force officials say they support Gates’ decision given budget constraints, but had pushed in the past for as many as 60 more, or a total of 243.

Creating an export version of the F-22 fighter would also keep the door open to a possible resumption of F-22 production for the U.S. Air Force in the future.

Japan for years has expressed interest in buying two squadrons of its own F-22s, which could translate into orders of 40 to 60 more airplanes for Lockheed.

Foreign sales of the F-22 fighter are banned under an amendment by House Appropriations Committee Chairman David Obey that was passed in 1998, but recent North Korean missile launches and continued interest by Japan in buying the F-22 may be softening congressional opposition, particularly since the F-22 production line is now nearing a shutdown.

The sources cited growing support for dropping the export ban, noting that tens of thousands of jobs were at stake around the country.

“There’s decent support, but it’s not a slam-dunk,” one said.

The source said it might be easier now to drop the export ban, given recent missile development activity by North Korea, the U.S. recession and strong U.S. ties to Japan.

Loren Thompson, analyst with the Lexington Institute, this week said Japan had expressed a willingness to pay the cost of modifying the sophisticated fighter jets for export.

Analysts say the bill for removing highly classified equipment could be close to $1 billion, but the prestige of owning and operating the world’s top fighter jet could make it a worthwhile investment for Tokyo. (Reporting by Andrea Shalal-Esa; Editing by Tim Dobbyn)