Concerns have grown that China could further restrict exports of the strategic minerals after it limited exports of germanium and gallium late last month.

Chinese authorities have instituted a range of measures to try to curb longstanding problems with illegal rare earths mining in recent years.

Export controls will be short-term disruptive to both gallium and germanium markets but Western countries should be able to adapt over time.

Eramet's CEO said China's show of force over the supply chain for key metals shouldn't come as a surprise.

The company said the manufacturing facility in Narva will be near its existing rare earth separation plant in Sillamäe.

The agreement establishes a 10-year offtake contract for minerals that NioCorp aims to produce at its Elk Creek project.

China said on Monday it will impose export restrictions on gallium and germanium.

The move underscores the dilemma facing President Xi Jinping as he seeks to counter US efforts to prevent China from accessing the chips needed to dominate technology.