WASHINGTON (Reuters) - Singapore has shown interest in possibly buying up to 100 of Lockheed Martin Corp's (LMT.N) F-35 Joint Strike Fighter aircraft over coming decades, matching Israel's tentative plans, the general in charge of the program for the Pentagon said on Monday.
Separately, the eight countries that have joined the United States to co-develop the plane appear to be largely sticking to their plans to buy some 730 of their own, said Air Force Maj. Gen. Charles Davis, the Pentagon's program chief.
"The Israelis have said they'd take up to 100 aircraft," he said in an interview. "The Singaporeans have said basically the same thing." Embassy spokesmen of the two countries had no immediate comment.
Development of the F-35, a family of radar-evading aircraft, was co-financed by Britain, Italy, the Netherlands, Turkey, Canada, Australia, Denmark and Norway.
The United States currently plans to buy a total of 2,443 F-35 models -- including 1,763 for the U.S. Air Force and 680 for the Marine Corps and Navy together. It is the costliest U.S. arms program ever at a projected $299 billion.
Hundreds of others may be sold overseas to replace a range of fighters, including Lockheed F-16s and Boeing Co (BA.N) F-18s.
Davis predicted Japan formally would request F-35 pricing and availability information by the end of this year as part of its next fighter selection process.
"There's no doubt it'll be a strong competitor" in Japan, he said, adding talks had also taken place with Spain about the F-35 as an eventual replacement for its Harrier jump jets.
He said the F-35 was on course to become a $1 trillion venture worldwide through 2065, when the last scheduled to be built would reach the end of its projected service life.
One trillion dollars is "what it costs to develop, buy, upgrade, sustain and fly more than 3,000 airplanes through their entire scheduled life cycle," he said, referring to the projected world fleet.
Tom Jurkowsky, a Lockheed Martin spokesman, said the F-35 program was making "outstanding technical progress, especially in the context of it being the most complex aircraft ever built."
The first F-35, a conventional take-off and landing version, began its flight testing program on December 15, 2006.
After the June 11 maiden flight of a short take-off, vertical landing model, the Pentagon's top arms buyer, John Young, said the program was more mature than comparable ones at this stage of development "in terms of quality, software, testing and manufacturing readiness."
Lockheed's chief F-35 subcontractors are Northrop Grumman Corp (NOC.N) and BAE Systems Plc (BAES.L). Two rival, interchangeable F-35 engines are under development. One is built by United Technologies Corp's (UTX.N) Pratt & Whitney unit; the other by a team of General Electric Co (GE.N) and Rolls-Royce Group Plc (RR.L).
F-35 competitors include Saab's (SAABb.ST) Gripen, the Dassault (AVMD.PA) Rafale, MiG-35 and Sukhoi Su-35, and the Eurofighter Typhoon, made by a consortium of British, German, Italian and Spanish companies.
Davis, in the interview, said his biggest concern was any "short-sighted decisions" to delay currently planned purchases of the aircraft, for which relative affordability is one of the hallmarks.
"Guys, quit screwing around with this," he said, spelling out his message to lawmakers holding the purse-strings in the United States and in the F-35 partner countries.
"We have a huge mountain to climb here," Davis added. He referred to going from current low-rate initial production of about 12 per year to 12 per month starting in 2014, when full production is due to kick in.
Around that time, the F-35A conventional take-off and landing version is projected to cost about $68 million apiece, he said. The F-35B short take-off, vertical landing model, designed for the Marines, would run about $85 million to $88 million, Davis said.
He put the cost per plane of the F-35C aircraft carrier variant for the Navy at $90 million to $92 million by around 2015. The F-35C version is due to fly for the first time in about October 2009, Davis said.
(Reporting by Jim Wolf; Editing by Tim Dobbyn)