By Siyi Liu and Dominique Patton

BEIJING (Reuters) -China, the world’s top processor of rare earths, on Thursday banned the export of technology to extract and separate the strategic metals, in a further step towards protecting its dominance in several strategic metals.

The commerce ministry sought public opinion last December on the potential move to add the technology to its “Catalogue of Technologies Prohibited and Restricted from Export”.

It also banned the export of production technology for rare earth metals and alloy materials as well as technology to prepare some rare earth magnets.

The catalogue’s stated aims include protecting national security and public interest.

China has significantly tightened rules guiding exports of several metals this year, in an escalating battle with the West over control of critical minerals.

It introduced export permits for chipmaking materials gallium and germanium in August, followed by similar requirements for several types of graphite since Dec. 1.

The move to protect its rare earth technology comes as Europe and the United States scramble to wean themselves off rare earths from China, which accounts for 90% of global refined output.

Rare earths are a group of 17 metals used to make magnets for use in electric vehicles, wind turbines and electronics.

China has mastered the solvent extraction process to refine the strategic minerals, which Western rare earth companies have struggled to deploy due to technical complexities and pollution concerns.

It is not clear to what extent the technology is actually being exported. China has discouraged its export since 2007, said a rare earths analyst, who declined to be named because of the sensitivity of the topic.

“Other countries like the U.S., Japan and France all have the separation technology but China has the top efficiency and cost advantage,” he said.

(Reporting by Siyi Liu, Dominique Patton and Beijing newsroom; editing by Toby Chopra, Jason Neely, Kirsten Donovan and Tomasz Janowski)