Exxon Mobil Corp (XOM.N) has rejected a contract offer from the United Steelworkers (USW) local chapter representing hourly workers at the company’s Beaumont, Texas, refinery and renewed its offer of a six-year contract, a union official said on Wednesday. Exxon has been campaigning for a longer agreement with the Beaumont workforce, offering first a five-year agreement and then a six-year pact.