General Motors Corp. (GM) and Ford Motor Co. (F) both reported 23 percent declines in October U.S. sales on Tuesday, as high gasoline prices further undercut demand for big sport utility vehicles.

In contrast, Japan's Toyota Motor Corp. and Honda Motor Co. Ltd. posted monthly sales gains of 5 percent and 4 percent, respectively. Toyota had the biggest U.S. retail market share in early October, according to a recent J.D. Power (search) survey.

The results at No. 1 worldwide automaker GM and Ford spread more gloom in Detroit (search), where domestic manufacturers have also been grappling with high labor and health-care costs and rising prices for raw materials and transportation.

Highlighting their plight, Moody's Investors Service (search) cut GM's debt rating deeper into "junk" territory on Tuesday, citing sliding market share and uncertainty about a turnaround at the struggling industrial icon.

Aftershocks from the recent hurricanes, fuel prices that are turning car buyers away from gas guzzlers and the lack of splashy new consumer incentives have been cited as factors that hurt U.S. vehicle sales last month.

But Ford and GM have problems attracting consumers that clearly seem to go beyond any seasonal, short-term issues. They have been bleeding market share to Toyota and other Asian rivals as some of their bread-and-butter vehicles lose appeal on Main Street.

Ford and GM can both take some solace, however, from the news that many other automakers also suffered a sales slump in October. Highly-publicized summer incentives, including so-called employee discount offers used to clear out 2005 model inventories, pulled many potential car buyers into the market earlier than they might have been otherwise.

The dreaded "pull-ahead" effect has cast a distinct autumn chill over many automotive showrooms, analysts said.

Uncertainty over jobs and the economy may also be putting a drag on vehicle demand, according to some analysts.

Nissan Down Too

Nissan Motor Co. Ltd. said its October sales fell 13 percent as it, too, took a hit from flagging demand for big SUVs and pickup trucks. Sales of Nissan's full-sized Titan pickup fell 30 percent while sales of the large Armada SUV were off 23 percent.

Chrysler said U.S. sales rose a wafer-thin 1 percent, giving the U.S. arm of DaimlerChrysler (DCX) 19 consecutive months of year-over-year gains.

All sales figures are adjusted one less selling day in October this year than a year ago and exclude the Detroit automakers' foreign brands.

Ford and GM are especially dependent on sales of pickups and SUVs, and are known for producing some of the industry's least fuel-efficient cars.

Ford said sales of some of its large SUVs, including the Explorer, Expedition and Navigator, fell more than 50 percent in October, compared with the same month last year, while its flagship F-Series pickup saw sales drop more than 30 percent.

Declines were similar at GM with October sales of models like the massive Hummer H2 SUV slipping 52 percent while the big Cadillac Escalade EXT fell 59 percent.

Analysts said U.S. light vehicle sales across the industry weakened to a seasonally adjusted annual rate of about 15 million units. That would be well below the 16.9 million rate in October last year and the lowest since August 1998.

George Pipas, Ford's main industry sales analyst, said he doubted the sales rate would improve much in November. Jim Press, Toyota's U.S. sales chief, said he sees industry-wide improvements in both November and December, however.

"I think December is going to be a great month," Press told Reuters. "There is a lot of inventory coming, new products. We will have a December to remember and forget October."

Pointing to a key cause of the lower October sales, industry tracking firm Edmunds.com said consumer incentives offered by automakers in the U.S. market dropped by an average of $589, or 22 percent per vehicle, in October compared with the same month a year ago.

It said incentives were the lowest since January 2003, when average incentives were $2,022 per vehicle. Among Detroit's automakers, Chrysler had the highest incentives at an average of $3,206 per vehicle, Edmunds.com said.