United Auto Workers President Dennis Williams said the union is working with General Motors (GM) to avoid layoffs as U.S. auto sales slump, AutoBlog reported.

GM is considering producing more trucks and SUVs while killing off six slow-selling models produced at underused car plants such as Hamtramck in Michigan and Lordstown in Ohio. It's unclear if the plants will start producing newer, more popular models.

Watch: Are you driving one of GM's most popular crossovers?

GM has cut shifts at several of its U.S. plants as inventories of small and midsized cars grow. If GM stopped producing the six models under consideration, it wouldn't happen until 2020. The models at risk are the Chevrolet Volt, Buick LaCrosse, Cadillac CT6, Cadillac XTS, Chevrolet Impala and Chevrolet Sonic.

GM stock traded down 0.7% by Tuesday's close.

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