CNN:

The United States, the European Union and Japan filed a trade case Tuesday over China’s export restrictions on minerals that are crucial for the production of many high-tech devices, according to EU and U.S. officials. The case aims to pressure China to lift export limits on certain minerals known as rare earths, a senior Obama administration official said.

China mines a huge percentage of rare earths used in high-tech manufacturing, and has gradually reduced the amount of material it will export. The United States claims China is hoarding the minerals; China defends its decision, and says its doing it out of environmental concerns and in-line with World Trade Organization (WTO) guidelines.