JOHANNESBURG (Reuters) - Striking workers at mid-tier South African platinum producer Northam Platinum have rejected the latest pay offer from the company, the National Union of Mineworkers (NUM) said on Wednesday. NUM said in a statement it had made an undisclosed counter proposal in a bid to end a stoppage that began in early November. The union said Northam's latest offer was for increases of between 9 and 9.5 percent while its latest published demands were for pay hikes of up to almost 40 percent.