Consumers will still have to wait a few years before they can swap the batteries of their cell phones for more environment-friendly fuel cells, the world's top handset maker Nokia said on Tuesday. "It is not a technology question, it is more like a supply-chain issue at the moment," Tapani Ryhanen, head of strategic research at Nokia Research Center, said at a seminar celebrating the center's 20th anniversary.

Ryhanen said the technology itself was already available and Nokia had tested it.

"A few years you would still need to wait," he said, adding that the industry had to sort out how to supply the fuel to consumers.

Fuell cells use a catalyst like platinum to start a electrochemical process to generates electricity from making oxygen react with a fuel such as hydrogen, ethanol or methanol.