U.S. defense officials are preparing a version of the stealth F-22 Raptor that Japan has expressed strong interest in buying.

While the Department of Defense is working to design an export version of the Raptor, U.S. Sen. Daniel Inouye, D-Hawaii, this week sent a letter to Japanese Ambassador the United States Ichiro Fujisaki saying that the F-22 would likely carry a price tag of $290 million.

Japan has made it known it would like to buy 40 F-22s, made by Lockheed Martin and Boeing, so the potential value of the deal is more than $11 billion.

Japan is looking to upgrade its air capabilities, which are anchored by 1970s-era F-4 Phantoms, made by McDonnell Aircraft and Mitsubishi, and F-15 Eagles, which was flew in 1972 after production by Boeing predecessor McDonnell Douglas.

It has taken some time for U.S. and Japanese negotiators to get a deal together for the F-22. And it will take several years of development to get an export version off the ground since there is a large amount of sensitive technology that U.S. officials believe needs protection. Aviation Week estimated it would be 2017 before delivery of the first aircraft to the Japanese air self-defense force.

Japanese defense officials are reportedly looking at other aircraft, including Lockheed's F-35 and the Eurofighter Typhoon, which is manufactured by a consortium of Alenia Aeronautica, BAE Systems and EADS. Neither have all the stealth capabilities of the Raptor, making them substantially less expensive. The Typhoon is estimated to be about $105 million per plane.

"We are still seeking the possibility of acquiring the F-22 but if that does not work out, we will have to consider not just the F-35, but others as options," Japanese Defense Minister Yasukazu Hamada told Kyodo News Agency. "As of today, we still want to seek the F-22."

The Japan Times said the Eurofighter group may be willing to sweeten the Typhoon deal by allowing Japanese manufacturers to take part in building the aircraft.

Inouye's letter is seen as a spotlight to keep attention focused on the F-22, but even with congressional and Japanese interest in a deal, it comes down to a decision by the Obama administration.

The Office of Management and Budget, a White House Cabinet-level office, suggested President Barack Obama turn back budget requests for additional F-22s, which could put a hole in production timelines and force the price to Japan even higher.