Japan's top three automakers Toyota, Honda and Nissan have united with Japanese energy firms in a push to commercialise greener hydrogen fuel cell cars and build a network of fuelling stations.

Along with 10 Japanese energy groups including natural gas refiners and distributors, the companies are aiming to build 100 filling stations by 2015 in Tokyo, Nagoya, Osaka and Fukuoka, the companies said in a statement Thursday.

The automakers are making a renewed push behind Fuel Cell Vehicles (FCVs), which covert hydrogen into electricity and emit nothing more harmful than water vapour.

The companies say that the creation of a hydrogen supply infrastructure network is crucial as manufacturers work to reduce the production cost of hydrogen-powered vehicles in order to make them commercially viable.

"Japanese automakers are continuing to drastically reduce the cost of manufacturing such systems and are aiming to launch FCVs in the Japanese market -- mainly in the country's four major metropolitan areas -- in 2015," they said.

"With an aim to significantly reduce the amount of CO2 emitted by the transportation sector, automakers and hydrogen fuel suppliers will work together to expand the introduction of FCVs and develop the hydrogen supply network throughout Japan."

The companies did not say how much they planned to invest in the project.

While all-electric vehicles such as Nissan's Leaf or hybrids like Toyota's Prius have hogged the limelight recently, fuel cells are seen as a more powerful alternative, but expensive production and a lack of a comprehensive fuelling network has been seen as prohibitive.

Toyota, pioneer of hybrids powered by a petrol engine and an electric motor, has said it plans to launch a fuel-cell car by 2015. It is applying its hybrid technology to the vehicles, swapping the petrol engine for a fuel-cell stack.

Honda in 2008 began delivering about 200 FCX Clarity hydrogen-powered cars on lease to customers in the United States, Japan and later in Europe.

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