Johannesburg - The National Union of Mineworkers (Num) said on Tuesday it had declared a dispute with miner Northam Platinum, accusing it of not bargaining, and said it would go to a mediator if further talks yielded no progress.The Num says it represents 89% of Northham's 8 000 workers, though the company says only a third of its employees belong to the union. Northham produces about 300 000 ounces of platinum group metals per year.A Num spokesperson said the union is seeking a 14% increase, almost triple the inflation rate, from Northham. The union said it is hoping to meet with the company on July 26.Northam spokesperson Marion Brower said if living allowance demands were included, the Num demands came to 25% and that "this was stalling the process. Management is not refusing to engage."She declined to say what the company was offering.Strikes loom across South Africa's key mining sector - including against world number one platinum producer Anglo American Platinum and in the gold and coal industries - as unions seek wage increases far above inflation.Mining houses say they can ill afford such hikes as they grapple with other soaring costs, and production disruptions in South Africa could push up the price of platinum and gold.