From DETROIT (Reuters) -- General Motors Corp, which filed for bankruptcy protection a week ago, said Monday that it would cease production of medium-duty trucks by July 31 after attempts to sell the operation failed.

"After four years of working with multiple potential buyers, General Motors has decided to wind down its medium-duty truck operations," the automaker said in a statement.

GM (GMGMQ) plans to cease production of Chevrolet Kodiak and GMC Topkick medium-duty trucks by July 31. The automaker sold about 20,000 of the vehicles last year, down from roughly 30,000 in 2007, as the U.S. economy sank into a deep recession.

Chief Executive Fritz Henderson told reporters at an event in Warren, Michigan, that the medium-duty truck the business had not been successful for years and workers would be deployed to other facilities or offered an attrition program.

GM has moved quickly since it filed for bankruptcy on June 1 to disclose plans for brands and operations not part of its long-term strategy. GM plans a quick sale of its profitable assets by the end of August to a new company.

Last week, GM said it had reached preliminary agreements to sell its Saturn brand to dealership group Penske Automotive Group and its Hummer brand to little-known Chinese heavy equipment maker Sichuan Tengzhong Heavy Industrial Machinery.

About 400 hourly and salaried workers are involved in the production of the medium-duty trucks at a GM plant in Flint, Michigan, spokesman Jim Hopson said.

The Flint plant has more than 2,100 employees overall and also builds light pickup trucks for GM. The automaker plans to continue production of the pickup trucks at the plant.

Navistar International Corp had been one of the potential buyers for the GM medium-duty truck operation. GM and Navistar had reached a tentative agreement on a sale, but the pact expired in August 2008 without a deal being reached.