Johannesburg - World number two platinum producer Impala Platinum said on Tuesday that if a 15-week strike continued at its local mines it would have to cut supply to clients to 40 percent of demand over the next three to four months.

Spokesman Johan Theron told Reuters the company had supplied customers with all of the metal they required until the end of April by drawing on inventories.

But its abilities to meet demand would soon match its production profile, currently 40 percent of normal output.

The wage strike by the Association of Mineworkers and Construction Union (Amcu) has also hit Anglo American Platinum and Lonmin and is the longest and most costly labour stoppage ever on South Africa's mines.

“Customers have accepted lower deliveries, so there is no contractual dispute,” Theron said.

“The difference between what we can supply and what they need they can source from the market themselves.”

Despite the unprecedented scale of the strike, which has hit 40 percent of global production of the precious metal used in emissions-capping catalytic converters in automobiles, the market's reaction has been muted.

Spot platinum is currently fetching $1,445 (R15,187) an ounce, slightly less than its levels on the eve of the strike by around 70,000 miners, as the market has anticipated that there are adequate above-ground stocks.

Wage talks collapsed almost two weeks ago, setting the stage for a protracted showdown between labour and business on South Africa's restive platinum belt.

Amcu has accused the companies of negotiating in bad faith and manipulating numbers to inflate the costs of higher wages. - Reuters