The Democratic Republic of Congo, the world’s leading producer of cobalt, has imposed a four-month ban on cobalt exports in an effort to curb market oversupply and stabilize falling prices. But the move has ignited a conflict between two of the country’s largest mining companies: China’s CMOC and Switzerland’s Glencore.

CMOC, the world’s largest cobalt miner, has urged the Congolese government to lift the ban before it expires on June 22. Company officials warn that the restrictions have led to sharply reduced inventories among their Chinese clients, raising concerns about potential disruptions to the supply chain for electric vehicle batteries.