American Rare Earths' (ASX:ARR) US unit, Wyoming Rare, will undertake additional mineral processing optimization tests at the Cowboy State Mine, part of the Halleck Creek Rare Earths Project in the US, according to a Friday filing with the Australian bourse.

The tests will evaluate multiple milling methods and optimise the beneficiation circuit, the filing said.

The company also plans to begin test mining in the near term to extract feedstock, the filing added.

Shares of the company fell past 1% in recent Friday trade.