Workers belonging to the United Auto Workers (UAW) at General Motors' Flint assembly plant in Michigan have narrowly voted against a proposed contract with the automaker, the union's local chapter said.

UAW Local 598 said in a Facebook post on Thursday that 51.8% of votes cast were against the proposed deal.

Union workers are voting on contracts from each of Chrysler-owner Stellantis, General Motors and Ford Motor, after the first coordinated strike against Detroit's Big Three automakers.

The vote at the Flint assembly plant, which manufactures the Silverado heavy duty pickup truck, comes after the Detroit Three automakers and the UAW reached tentative deals over the last few weeks to end a costly strike following marathon negotiations.

The UAW's new agreement, which covers 46,000 workers overall at GM, grants a 25% increase in base wage through April 2028 and will cumulatively raise the top wage by 33% compounded with estimated cost-of-living adjustments to over $42 an hour.

Automakers had previously been slashing costs and navigating a bumpy road to manufacture EVs and catch-up with market leader Tesla. However, lower margins on those vehicles have deterred them from accelerating the move.

GM in October pulled its full-year profit forecast and postponed a $4 billion electric truck plant in Michigan.

(Reporting by Nathan Gomes and Shivansh Tiwary in Bengaluru; Editing by Sriraj Kalluvila)