DETROIT (AP) — The U.S. automotive sales slump worked its way to two Midwestern automaking towns Monday when General Motors Corp. announced it would close a Michigan metal stamping plant and stop making sport utility vehicles in Wisconsin by the end of the year.

Workers at the Grand Rapids Metal Center in suburban Wyoming were told it will close by the end of 2009. The plant employs about 1,340 hourly and 180 salaried workers.

Earlier in Janesville, Wis., workers got the news that SUV production at the plant, with 1,200 employees represented by the United Auto Workers, will end Dec. 23. The closure is earlier than GM had expected but was necessary because of declining sales, GM spokesman Chris Lee said.

The Grand Rapids plant was picked for closure because more than 40 percent of its parts go to slow-selling truck and SUV plants, and because it is far from GM vehicle assembly factories, Lee said.

GM wants to cut shipping costs by keeping its stamping plants closer to assembly plants, he said.

“Unfortunately Grand Rapids is some distance away from their assembly plant customers and therefore doesn’t really support that strategy that we’re moving toward,” Lee said.

Lee would not say whether more plant closures were expected, but said GM “will continue to assess our stamping capacity and align it with market demand as required.”

The closure in Grand Rapids stunned workers who thought they were safe because the plant had won safety and productivity awards, said United Auto Workers Local 730 President Greg Golembiewski.

“I am sick about what’s happened here,” he said. “I am devastated. I’d like not to believe what I heard today. It’s like a bad dream.”

He said the company’s explanation for the closure was simply that it was a business decision.

In Janesville, the factory also has a small- to medium-duty truck production line with 35 to 50 workers. They will keep working until they have filled an order for Isuzu Motors Ltd., which should take the plant through May or June, Lee said. Then the plant “will cease operations completely,” he said.

Workers at both plants will get most of their pay from the company and unemployment benefits for up to two years under their union contract. They will have the option of transferring to other GM factories if jobs are open. Other conditions of their departure may be negotiated with the union, Lee said.

Most of the Janesville factory makes the GMC Yukon and the Chevrolet Tahoe and Suburban large SUVs, and sales of those vehicles have plummeted with an increase in gasoline prices to around $4 per gallon earlier this year. Gas prices have subsided closer to $3 per gallon nationwide, but that has done little to boost sales.

“That segment is really shrinking, so we had to make the difficult decision to have this cessation,” Lee said.

GM announced in June that it would close Janesville and three other factories as demand for pickup trucks and SUVs waned, but the only time frame that was given was by 2010. The company announced earlier this month that another of those plants — the Moraine, Ohio, SUV factory — will close Dec. 23.