Rare earths now a weapon in Bejing's arsenal

RARE earths, a group of 17 metallic elements including yttrium, lanthanum and gadolinium, are used in small quantities to enhance batteries, computer and weapons systems, and are generally found together.

China has gradually, over several years, reduced their export through a quota system designed to keep more of them for its own industries.

Media sources in China have recently quoted researchers speculating that choking off exports of rare earths to Japan would be an option open to the government in the dispute over the trawlerman's arrest.

"Japan has a great need for these resources from China, reducing or restricting resource exports to Japan would be a useful measure," The Global Times reported ministry of commerce researcher Tang Chunfeng as saying.

The trawler dispute is just part of a wider issue over the ownership of islands in the East China Sea, called Diaoyu by the Chinese, and Senkaku by the Japanese. Japan currently controls them - and as such would have access to any oil and gas reserves in the surrounding seabed.