Apple Inc is talking to major cobalt producers to secure supplies of the material vital for the lithium-ion rechargeable batteries that power its mobile phones, three cobalt industry sources said.

But Apple declined to comment.

Locking in cobalt supplies has become a dominant theme as it is also used in batteries to power electric vehicles whose rapid growth is revolutionizing the motor industry, which is also looking to agree on long-term supply deals.

Automakers, mobile device makers and manufacturers of super-alloys used to make jet engines are all getting jittery about possible scarcities of responsibly sourced cobalt, sources said.

“We’re not sure whether (Apple) want to buy the cobalt for the battery makers that supply them or whether they are planning to stand behind the cobalt supply chain as guarantors,” a cobalt industry source said.

“They’ve been asking producers to make offers. We’re not sure of the volumes, but if they are looking for anything more than a couple of years, they might be disappointed.”

A Bloomberg report, citing an anonymous source, said the iPhone maker was seeking contracts to buy several thousand metric tonnes of cobalt for five years or longer.

Industry sources said Apple had spoken to miners such as Glencore, a top producer, which said late last year it would produce around 39,000 tonnes of cobalt this year.

Asked on a result call with reporters on Wednesday about the company’s relationship with Apple, Glencore’s Chief Executive Ivan Glasenberg said: “We have not signed any deals,” adding that Glencore would not sign any long-term deals because the company did not want to lock in cobalt prices.