(Adds schedule details, comments from Bodgan, Marine official)
By Andrea Shalal
WASHINGTON, March 26 (Reuters) - The software needed for the U.S. Navy's version of Lockheed Martin Corp's F-35 fighter jet could be delayed by four to six months, the U.S. general who runs the $392 billion program for the Pentagon said on Wednesday.
Air Force Lieutenant General Chris Bogdan also told lawmakers the earlier Block 2B software was about 80 percent complete and, while he was "pretty confident" it would be ready in time for the Marine Corps to start using its B-model jets in combat by mid-2015, a 30-day delay from July 1, 2015, was possible.
The Pentagon's chief weapons tester and the congressional Government Accountability Office have both warned that slow software development could delay the adoption of the aircraft by the Marines and other U.S military branches.
Bogdan has said for some time that he is less confident about completing the software needed for the Navy to start using the jets in combat in 2018. Wednesday marked his first detailed forecast for how long that work could be delayed, beyond the current target of August 2017.
There had been changes to accelerate software development and the schedule for the Block 3F software needed by the Navy could still be achieved.
"There are a lot of things I can do between now and 2018," Bogdan said. "I'm just projecting that we're going to have some trouble getting it done."
Bogdan later told reporters there was no need to bring in outside consultants as was done to help fix the F-35's computer-based logistics system.
He told the tactical air and land forces subcommittee of the House Armed Services Committee that he was more concerned about retrofitting F-35B jets already built for the Marine Corps with 96 engineering changes.
Lieutenant General Robert Schmidle, deputy commandant of the Marine Corps for aviation, echoed Bogdan's concerns, but said the Marines hoped to save time by doing some of retrofitting at the Yuma, Arizona, base where they currently fly the jets, instead of moving them to a depot.
Bogdan said pending decisions by Italy, Canada and Turkey to delay or reduce their F-35 orders could raise the cost of each remaining aircraft by 2 to 3 percent.
Lockheed is developing three models of the warplane for the U.S. military and eight countries that helped fund its development: Britain, Canada, Australia, Turkey, Italy, Denmark, Norway and the Netherlands.
South Korea said this week it would join Israel and Japan, two other countries outside the initial group, which have also ordered the jets.
Representative Loretta Sanchez of California, the top Democrat on the subcommittee, quizzed Bogdan about news the international partners had provided $400 million in extra development funding.
Bogdan said the money came from savings achieved during earlier phases of the program, and helped offset the injection of billions of dollars by the U.S. Defense Department when the program was restructured.
Bogdan said the program was also working closely with Lockheed and Pratt & Whitney, a unit of United Technologies Corp , to improve the jet's reliability. By 2015, current reliability rates could rise by 60 percent, he added.
(Reporting by Andrea Shalal. Editing by Andre Grenon)