Negotiations will resume on Wednesday between Royal Dutch Shell Plc (RDSa.L) and union leaders as they haggle over a new wage contract for striking U.S. refinery workers, the company said. The two camps have been at an impasse since the United Steelworkers union (USW) called walkouts early on Sunday for the first time since 1980 at nine plants with about 10 percent of U.S. refining capacity, saying Shell left the negotiating table when talks broke down.