The trading unit of CMOC Group — the world’s biggest producer of cobalt — has declared force majeure on deliveries of the battery metal, after the Democratic Republic of Congo extended a ban on exports.

Congo — which accounts for about three-quarters of global cobalt supply — initially suspended exports for four months on February 22, before extending it by three further months earlier in June. Cobalt prices have slumped in recent years on the back of surging output in the country, particularly from two large mines operated by China’s CMOC.

IXM SA, which is owned by CMOC, “formally declared force majeure under its cobalt supply contracts due to the ongoing export ban,” the trading house said in a statement on Monday, confirming an earlier Bloomberg report. The halt to shipments has “rendered it legally and practically impossible” for CMOC’s copper and cobalt mines to supply IXM, it said.

While Congo said it prolonged the measures “due to the continued high level of stock on the market,” IXM’s actions show the increasing strain on flows of cobalt hydroxide, the main product exported from the central African nation. So-called force majeure clauses allow companies to suspend deliveries because of events beyond their control.

A spokesperson for CMOC confirmed the decision taken by IXM, while the Congolese regulatory body overseeing the ban didn’t immediately respond to a request for comment.

Congo’s government wants to exert greater influence over cobalt prices by aligning supply with global demand. Analysts have warned that too-stringent controls and soaring prices could hasten a shift by manufacturers toward EV batteries that don’t use the metal. CMOC has made similar arguments to the authorities.

The largest producers of cobalt after CMOC are commodities giant Glencore Plc and Kazakhstan-backed Eurasian Resources Group Sarl, which both own major assets in Congo. Telf, the marketing agent of ERG’s cobalt, declared force majeure on supply contracts in March.

“As the global cobalt supply chain faces heightened volatility, IXM remains committed to navigating this disruption responsibly,” the trading firm said in the statement.