The ongoing action at the Stillwater mine will affect the supply of platinum and palladium, Stillwater Mining's chief executive has confirmed.

Frank McAllister's warnings came after the industrial action continued since Monday's shut-down, with the CEO and chairman saying there would be a reduced supply of both metals being shipped to the company's customers.

Mr McAllister told Dow Jones that because the company's supply contracts are on a percentage-of-production basis, the stall in production would inevitably have an impact.

However, he did identify some "pipeline inventory" that was yet to be processed by external fabricators, which he hoped would meet the short-term commitments.

He also remained upbeat about the prospects for conciliation, saying that the two sides had "had a disagreement but are willing to get together and talk again".

If the strike continues, however, McAllister acknowledged the problems could worsen.

Union workers at the Stillwater Mining Company went on strike after voting against a proposed three-year wage agreement.

Around 850 underground mine and processing employees took action, after an initial wage agreement between management and the Paper, Allied Industrial, Chemical and Energy Workings International union fell apart.