Union workers at Nexteer Automotive's complex in Saginaw, Michigan, walked off the job after rejecting a proposed contract, halting production of steering systems and other components essential to vehicle production by General Motors Co and other automakers. United Auto Workers union Local 699 announced the strike on its Facebook page. The action came after workers at the Saginaw factory voted down a proposed contract by a wide margin. Local 699 leaders posted a tally sheet of the vote on Facebook. GM was assessing the potential impact on its operations, a spokesman said. Nexteer, controlled by a unit of Aviation Industry Corp of China, was formerly part of GM, and remains a major supplier of steering systems and related hardware to the Detroit automaker. Nexteer supplies steering systems for GM's profitable large Chevrolet Silverado and GMC Sierra pickup trucks. "We are trying to resolve this as quickly as possible," Nexteer spokesman Luis Canales said in an interview. A spokesman for UAW leadership in Detroit did not have an immediate comment. Officials at Local 699 could not be reached.