Sept. 2 (Bloomberg) -- General Motors Corp., battling an 18 percent decline in U.S. sales this year, plans to offer employee discounts to all customers for four more weeks, people familiar with the plans said.

The incentives, on most 2008 and some 2009 models, were to have expired today. GM will continue the deals through the end of the month after the initial two-week offer boosted sales, said the people, who didn't want to be identified because GM hasn't made its strategy public.

GM is extending the profit-lowering discounts after its U.S. truck sales dropped 23 percent through July in the face of $4-per-gallon gasoline and plunging consumer confidence. The automaker's U.S. sales drop has been wider than the industry's and contributed to $18.7 billion in first-half losses.

``They have an unbelievable amount of trucks in inventory, and they need to get rid of them,'' said George Magliano, director of automotive research for Global Insight Inc. in New York. ``With the 2009 models coming in, GM has no choice but to juice the deals.''

The program allows all U.S. customers to pay the same prices as employees at Detroit-based GM. Under the current offer, a Buick Enclave sport-utility vehicle costs $30,949, compared with a manufacturer's suggested retail price of $33,955, according to GM's Web site.

John McDonald, a GM spokesman, declined to comment.

More Inventory

GM's U.S. inventory of cars and light trucks rose by 11 days to an 82-day supply on Aug. 1 from a month earlier, compared with 69 days for the industry, according to trade publication Automotive News.

Dealers reported ``some resurgence'' in demand for larger SUVs and pickups this month, Vice Chairman Bob Lutz said on Aug. 28. Vans, pickups and SUVs account for about 56 percent of GM's U.S. sales.

GM, which reports August sales results tomorrow, may say demand fell 29 percent during the month, according to a Bloomberg survey of 5 analysts. The company hasn't posted an annual U.S. sales gain since 1999 or an annual profit since 2004.

Employee discounts vary by vehicle and bring the price closer to the dealer's invoice amount. GM introduced the deals in June 2005 and boosted sales 47 percent that month, forcing U.S. rivals Ford Motor Co. and Chrysler LLC to follow suit.

GM, the largest U.S. automaker, pared its average incentive per vehicle in July by 3.9 percent from June to $3,284, according to Autodata Corp. in Woodcliff Lake, New Jersey. The industrywide average fell 1.4 percent to $2,773, Autodata said.

Last month, GM allowed its U.S. employees to extend their discounts to friends or extended family on a one-time basis before beginning the current program on Aug. 20.

GM gained 65 cents, or 6.5 percent, to $10.65 at 4:15 p.m. in New York Stock Exchange composite trading. The shares dropped 57 percent this year.

To contact the reporter on this story: Greg Bensinger in New York at gbensinger1@bloomberg.net

Last Updated: September 2, 2008 17:43 EDT