General Motors Corporation said Thursday it will temporarily shut down 13 assembly plants in the United States and Mexico between May and July, a move that will take 190,000 vehicles out of its production schedule.

GM said the shutdowns wouldn't affect operations that are in the process of launching new products, including the new Chevrolet Camaro built in Oshawa, Ont., and the Buick LaCrosse (called an Allure in Canada) launching soon at its assembly plant in Fairfax, Kan.

GM said its Canadian plants would take their usual two weeks of summer downtime during the weeks of June 29 and July 6.

It was not immediately clear what effect the summer shutdown would have on GM's engine plant in St. Catharines, Ont., or its transmission plant in Windsor, Ont. Both plants feed parts to U.S. facilities, said Chris Buckley, the president of Canadian Auto Workers Local 222.

"Obviously there will be an impact to the city of St. Catharines and the city of Windsor, but we're not sure what that amounts to as of today," Buckley said.

Laid-off hourly workers will get unemployment benefits and supplemental pay from the company that amounts to most of their base wages.

Salaried workers also will get some income, GM North America president Troy Clarke said.

In a conference call with reporters Thursday, Clarke said the shutdowns are not a sign that GM is headed into bankruptcy protection.

Clarke would not say exactly how many workers would be laid off; nor would he say if any of the factories would be closed for good.

GM has told the government it plans to close five more factories as part of its restructuring plan, and its CEO said additional closures are possible.

The company's U.S. will plants will take the customary two weeks of summer downtime, plus anywhere from one to nine weeks of extra shutdown time.

GM said the extra shutdowns will help reduce its U.S. dealer inventory level to 525,000 vehicles by the end of July. At the end of March, there were approximately 767,000 vehicles in its U.S. dealer stock.

"While sales have been performing at or close to our plan estimates, and dealer inventories have been reduced accordingly, we want to more closely align inventories with even more conservative market assumptions," Clarke said in a statement.

"By reducing our inventories even more aggressively we reduce pressure on GM and our dealers, and set ourselves up well for a clean 2010 model year startup."