JOHANNESBURG, Dec 1 (Reuters) - The South African government has requested the postponement of a court hearing on Wednesday over a critical wage dispute with public sector trade unions, a letter sent by the state attorney’s office to the unions’ lawyers showed. But the Public Servants Association and unions affiliated with the COSATU federation told Reuters they were opposed to the hearing being postponed. (Reporting by Alexander Winning and Wendell Roelf; Editing by Alison Williams)