Toyota, the world's second-biggest car maker, believes launching hydrogen cars earlier than 2015 would be difficult due to a lack of filling stations, the paper said.

Its plans are more conservative than those of General Motors Corp., which aims to have a production-ready hydrogen vehicle by 2010 with a fuel cell that costs $5,000, it said.

Hydrogen fuel cell vehicles, which emit only water, would ease environmental concerns and help cars meet stricter emissions regulations. They could also counter to rising energy prices.

A Toyota spokesman could not confirm Okamoto's comments.

Toyota said on Friday its fuel-cell hybrid cars had received vehicle type certification from the Japanese government -- meaning the cars no longer need to be certified individually -- clearing the first hurdle for commercialisation.

Toyota, which started limited marketing of fuel-cell vehicles in 2002, has now leased 16 such cars to government bodies in Japan and the United States but has not revealed any launch plan.