The World Trade Organization confirmed that China had lost a case on rare-earth metals, the latest setback for Beijing in a dispute marked by price spikes and widespread concern among technology firms and defense-related users of the critical materials.

The Geneva-based trade body and the office of the U.S. Trade Representative, which brought the original case two years ago, confirmed China's policies were found to violate global trade rules. The announcement comes almost five months after Chinese officials said they had lost the case, and four months after the deadline for the WTO to inform the parties involved in the case.

The WTO said China's export duties on rare-earth metals, molybdenum and tungsten are inconsistent with its obligations in the organization. It also ruled against Beijing's export quotas on the materials and its move to restrict their trade.

China has said the restrictions are in place for environmental-protection reasons. The WTO ruling said those aren't valid reasons for limiting exports. Rare earths are the metals at the bottom of the periodic table that are particularly useful in many high-tech applications such as , from lasers to solar panels to electric-car batteries to and smartphones.

The ruling covers 17 rare-earth materials such as thulium, ytterbium and lutetium that are used in electronic and high-tech products. It also covers tungsten and molybdenum, which have many industrial uses.