Cerrejon, owned equally by Glencore, BHP Group and Anglo American, has been in negotiations with its largest union and on Wednesday said that "significant advances" had been made.

Glencore's year-to-date coal production is 83.5 million tonnes, which is down 20% from a year earlier.

The mining and trading giant maintained its 2020 guidance for all its other products.

Glencore's copper production was 934,700 tonnes year to date, 8% lower than a year earlier, while cobalt production of 21,600 tonnes was down 37%, due to the shuttering of its Mutanda mine in the Congo.

Glencore subsidiary Katanga Mining's Kamoto Copper Company mine in the Congo is ramping up to full production, and should produce 270,000 tonnes of copper as cathode this year, head of Africa copper Mark Davis said last month.

"Glencore has delivered a solid third-quarter operating performance, including the continued successful ramp-up of Katanga, which remains on track to achieve design capacity by year-end," CEO Ivan Glasenberg said.

(Reporting by Helen Reid; editing by David Goodman and Jason Neely)