South African platinum miners on Thursday begana strike that threatens to cripple production at the world's threetop platinum producers, dpa reported.The trade union Amcu said its 70,000 members would remain on strikeuntil their pay demands are accepted.The union is demanding an entry-level monthly "living wage" of 12,500rand (1,143 dollars), double what the miners currently earn.The mining companies Anglo American Platinum, Impala Platinum andLonmin Platinum say they cannot afford the increase as they grapplewith increased costs and lower metal prices.South Africa has more than 80 per cent of the world's platinumreserves and is the fourth-biggest gold exporter.