The proposal, signed by companies responsible for 85% of the DRC's copper, cobalt and gold output, suggest that sliding royalties will give the government a higher share of revenues.
Company has agreed to sell its 80% stake in the Kestrel mine to a consortium comprising of private equity manager EMR Capital and Indonesian coal company Adaro Energy.
The maintenance activity, originally scheduled for April, comes amid media reports that thousands had taken to the streets and shut shops in Thootukudi to protest against the expansion of the smelter.