Boeing and Mitsubishi Heavy Industries, which is developing Japan's first passenger jet, said they're in talks about collaborating on the project.
Mitsubishi Heavy, Asia's biggest aerospace company, is developing a 70- to 90-seat plane called the Mitsubishi Regional Jet and planning the first flight for 2012.
Takashi Nishioka, the company's chairman, asked for Boeing's help last month.
"We're discussing the possibility of cooperation," Naoko Masuda, a Boeing spokeswoman in Tokyo, said Wednesday.
The U.S. plane maker won't invest in the project, she said, declining to say what is being discussed.
Hideo Ikuno, a spokesman for Tokyo-based Mitsubishi Heavy, said the companies are "in discussion" and wouldn't elaborate.
Japan's Asahi Newspaper reported earlier Wednesday that Boeing is considering investing in the project, which may cost as much as $3.3 billion. The paper cited an interview with Nobuo Toda, Mitsubishi Heavy's head of aerospace.
The Japanese manufacturer seeks to attract international airlines with a jet designed to be 20 percent more fuel efficient than existing models.
It plans to use carbon-fiber composite material similar to what it uses in the wings it makes for Boeing's new 787.
Japan is stepping up efforts to resume production of domestically built planes, the first since the propeller-powered YS11 that first flew in 1962.
Kawasaki Heavy Industries said Tuesday it's considering developing a commercial version of a cargo plane being designed for Japan's military.
Boeing and Airbus dominate the market for planes of more than 100 seats. Bombardier of Canada and Embraer of Brazil lead in the market for smaller aircraft.
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