Resale value of brands that might be sold by General Motors is falling faster than the industry average, casting more doubt on them, a leasing guide said.

New Hummer, Saab and Saturn sales are already suffering after GM vowed to sell or close them by 2011 as part of its survival plan, Dow Jones said.

The Saab and Hummer brands both suffered double-digit percentage declines in February, compared with the average for the first nine months of 2008, according to Automotive Lease Guide.

Residuals across the US industry were down just 1% over the same period, helped in part by a decline in auto auction activity as rental companies cut new orders and held onto cars for longer, the report added.

Combined sales of Saab, Saturn and Hummer sank 59% in February, more than GM's 53% overall decline. GM sales chief Mark LaNeve said GM's strategic review of the brands was "understandably" hurting sales.

"There's a lot more uncertainty in what the future holds for these brands," Automotive Lease Guide general manager James Clark said.