General Motors is reported to be offering its US dealers a cash incentive of 1% on each 2009 model year vehicle they sell.

The 'marketing stimulus payments' would be made six months after a vehicle is sold and would be computed from the base-model invoice price, three sources told Bloomberg News, requesting anonymity as the scheme had not been made public. The programme would run to the end of this year, they said.

The report said dealers - GM has about 6,500 in the US - would receive hundreds of dollars per vehicle under the programme - the payment, for example, would be US$166 on a GMC Sierra pickup truck and $549 on a Hummer H2 SUT sport-utility vehicle, based on base-model invoice prices of $16,623 and $54,940.

GM spokesman John McDonald told the news agency the automaker did not disclose dealer incentives. Most 2009 models would have reached showrooms by the end of October, he added.

The Detroit-based brands GM, Ford and Chrysler collectively posted a 21.5% sales fall to 508,367 units in September and were 19.4% down to 5,150,408 year to date, according to WardsAuto.com data (which is adjusted for monthly selling days).

Ford took the biggest tumble last month - 31.2% to 118,401 - followed by Chrysler (-30.2% to 107,061) and GM (off 12.1% to 282,869).

To the end of the third quarter, Chrysler sales were down 25.3% to 1,179,517 units, Ford was down 17.2% on 1,557,114 and GM sales had softened 17.8% to 2,413,525.

GM's decline was less last month as the automaker offered all customers 'employee discount' prices, Bloomberg said.

"GM seems to be trying to get dealers to try to order more vehicles and give them an incentive to really sell more between now and the first payment,'' AISrebates president Troy Ontko told Bloomberg. His Michigan company tracks US auto industry offers.

Edmunds.com, one of a number of firms which tracks automakers' incentive spending, calculated that GM spent $3,972 per vehicle on 'spiffs' last month compared with $4,053 in August and $3,132 in September '07.

"In September 2008, the industry's aggregate incentive spending is estimated to have totalled approximately $2.94bn, down 15.8% from August 2008," Edmunds said.

"Chrysler, Ford and General Motors spent an aggregate of $1.98bn, or 66.7% of the total; Japanese manufacturers spent $639m, or 21.6%; European manufacturers spent $238m, or 8.0%; and Korean manufacturers spent $108m, or 3.7%."

Plunging dealer profitability is a major concern in the world's largest car market where recent casualties include a bankruptcy protection filing by the largest Chevrolet dealer chain, Bill Heard Enterprises, on 28 September.

The current 'credit crunch' means customers cannot get financing for vehicles they want to buy and dealers are having problems obtaining the funds they need to keep their outlets open.

Bloomberg noted that GM's US sales head, Mark LaNeve, said on 1 October that the company's partly owned financing arm, GMAC, was monitoring dealer profitability as leasing fell to less than 1% of all sales.

On Tuesday, as she urged the federal government to implement the US$700bn economic recovery plan as quickly as possible, National Automobile Dealers Association (NADA) chief Annette Sykora said: "We're likely to lose up to 700 dealerships this year. Some of these [closings] stem from the challenges faced by the Detroit Three."