The suspension has been equated to 25% of global supply being delayed until the second half of 2019.

"The market will still be oversupplied next year as they are planning to make up sales in the second half and there are many others selling cobalt hydroxide," Macquarie analyst Vivienne Lloyd told Reuters.

BMO Capital Markets analyst Colin Hamilton told the wire service they had been forecasting the largest cobalt surplus on record for 2019, albeit in a market with 13% consumption growth.

"Taking out the planned 30,000 tonnes of mine supply from Kamoto, however, leaves first half 2019 in the largest deficit on record," he told Reuters.

"But should Kamoto play catch-up in the second half, we would have an aggressive swing to surplus."

Katanga is planning to build a US$25 million ion exchange system to remove uranium from the mine's cobalt after levels were detected above the acceptable limit for export.

The system is expected to be commissioned by the end of the second quarter 2019, subject to Katanga obtaining the necessary approvals.

The cobalt spot price has tumbled since a peak at US$94,800 a tonne in March and last traded at $55,000/t, little changed since the Kamoto suspension.

However Katanga shares, which started the year above C$2, have hit a 52-week low and closed at 43c yesterday, capitalising it at $820 million.