Congo, the world's leading producer of cobalt and Africa's biggest copper producer, banned exports of copper and cobalt concentrates in 2013 to encourage miners to process and refine the ore in the country.

But insufficient smelting capacity has driven it to repeatedly issue waivers. In August, the government granted an indefinite moratorium for all minerals exports except copper concentrate, pending discussions with miners.

"This moratorium, which will end on April 12, 2021, can only be extended on the justification of a project for further processing on site," Mines Minister Willy Kitobo Samsoni said in a letter to other members of the government dated Oct. 12.

(Additional reporting by Stanis Bujakera; Reporting by Hereward Holland; Editing by Edmund Blair and Mark Potter)