Detroit ? General Motors Corp. told its dealers Tuesday that it will force 1,000 to 1,200 underperforming locations to close their doors as the automaker tries to thin dealer ranks to make the remaining outlets more profitable.

GM told the dealers about the plan in a video conference, according to a dealer who spoke on condition of anonymity because the video conference was private. It is part of the company’s plan announced Monday to cut more than 2,600 dealers by 2010.

The company expects to lose 500 Hummer and Saturn dealers when those brands close or are sold, and it expects 400 dealers to close voluntarily. Another 500 would be consolidated into other dealerships, according to the dealer.

GM said Monday that it also would eliminate its Pontiac brand, but there are only 27 dealers that sell just Pontiacs, according to the National Automobile Dealers Association. Most Pontiac dealers also sell Buick and GMC vehicles at the same location.