The UN's environment chief on Wednesday called for a global drive to recycle rare metals that have hit the headlines in a spat between Japan and China, warning that they are crucial for green technologies.

Achim Steiner, executive director of the UN Environment Programme (UNEP), said that demand for "rare earth metals" such as lithium and neodymium -- used in batteries for hybrid cars or components in wind and solar power -- was accelerating fast.

Rare earths are available in only small quantities and mined in a few locations, raising fears that global supply for a clean, high-tech economy could be exhausted swiftly as well as hampered by geopolitical disputes.

"There is both a strategic as much as an environmental or an economic rationale to rapidly look at making these metals part of a recycling economy," Steiner told reporters, insisting on the need for an economically stable green tech industry.

There is "an immense increase in demand for rare (earth) metals that are central to the green and high tech economy future... from the electronics industry, car industry and energy industry," he said.

Industry sources said yesterday that China has moved towards resuming exports of rare earths to Japan that were disrupted by amid a bitter territorial dispute in recent weeks.

Beijing has repeatedly denied claims it blocked the shipments of rare earths, which Japan's crucial high tech electronics and manufacturing industry rely on.

A UNEP-hosted panel of experts highlighted the concerns about rare earth or speciality metals in May, estimating that only one per cent was recycled at the end of a product's life while the rest was discarded.

By comparison, the International Panel for Sustainable Resource Management estimated that common metals such as steel, aluminium, copper and tin have 25 to 75 per cent recycling rates, in some instances exceeding fresh raw material supplies from mining.

Steiner said that, based on current knowledge, some rare earths "may be exhausted, as with peak oil, on a time horizon of 30 to 40 years."

Officials said supplies of such rare metals were confined to a limited number of countries, including Australia, China, Venezuela, Bolivia and the United States, while extraction was complex and costly.