By Ed Stoddard and Zandi Shabalala JOHANNESBURG (Reuters) - World number-one platinum producer Anglo American Platinum (J: AMSJ ) is to sell a swathe of its most labour-intensive South African mines after a five-month strike shattered its hopes of ever making them profitable. The mines account for over half of the company's workforce but only a quarter of production and their viability was dealt a blow when miners won pay increases of up to 20 percent. Amplats said it would now focus on its more mechanised mines. For the miners who faced hardship in their campaign for better pay, a sale could increase the risk of future lay-offs. The buyers are likely to be companies with a focus on deep-level, labour-intensive mines, which may have more appetite than Amplats for the challenge of making them commercially viable. One of the biggest hurdles will be stiff opposition to any job cuts from unions and politicians.