Katanga shares, listed in Toronto, fell around 20 percent by 1654 GMT, while Glencore fell nearly 3 percent in London trade.

To remove uranium found in levels above the acceptable limit for export, Katanga plans to build an Ion Exchange system, at a cost of around $25 million.

It said it should be completed by the end of the second quarter of next year, provided it obtains the necessary permits.

So far, the production affected by the suspension amounts to 1,472 tons of finished cobalt, which will be stockpiled.

Cobalt prices have fallen nearly 40 percent this year after Chinese refiners began producing the metal and there was no immediate cobalt market reaction to Tuesday's news.

Tyler Broda, analyst at Royal Bank of Canada, which rates "Glencore" outperform, said the delay in cash generation as around three quarters' worth of cobalt production piles up in Congo, should be offset by increased revenues from cobalt produced in Glencore's other mines.

"Depending on the magnitude of any price reaction on the wider cobalt market, this could, perversely, work out to be an economic benefit for Glencore," Broda said in a note.

Credit Suisse analysts, which also rate Glencore "outperform," in another note said the only material impact was the $25 million cost of the ion exchange system and revenues from cobalt sales were only being deferred.

Glencore has previously said it expected sales of around 65,000 tonnes in 2019, with Katanga making up around 34,000 tones of that. The world cobalt market is around 120,000 tonnes.

(Reporting by Barbara Lewis in London and Debroop Roy in Bengaluru; Additional reporting by Pratima Desai; Editing by)