U.S automobile sales ran out of gas in July as major American auto producers posted negative growth in the number of cars and trucks they pushed off the lot in the month.

And the carmakers were already warning that conditions in the industry could get even worse.July sales slump for big U.S. carmakers M. Spencer Green/AP

“We expect the second half of 2008 will be more challenging that the first half as economic and credit conditions weaken,” Ford's marketing chief Jim Farley said in a statement on Friday.

The biggest loser was General Motors, which saw its sales of light trucks drop 35 per cent in July. The company's SUVs and pickups were snubbed by consumers who are seeking more fuel efficiency as opposed to driving power.

GM, which posted a $15.5 billion US quarterly loss on Friday, said car sales also slipped, down 12 per cent.

Car-sales tracker Edmunds.com had expected GM sales to fall by only 16 per cent.

GM did much better in Canada.

In this country, the company posted a five per cent increase in sales last month versus July 2007. The Chevrolet Malibu and Pontiac G6 were among the GM vehicles that popped July gains in Canadian sales.

The U.S. story was similar at Ford Motor Co., where flagging truck and SUV sales pulled the company's overall monthly sales down by 15 per cent. Ford's light truck sales, where the Ford, Mercury and Lincoln brands are crucial, were off 26 per cent.

Ford did manage to post flat sales on the car side of the business, led by a 16 per cent bump-up in sales of its fuel-stingy Focus.

The July results of Ford Motor Co. of Canada were off by almost the same amount, down 13.9 per cent, as in the United States.

Japanese carmakers not immune

Even the Japanese carmakers, long seen as able to weather the turbulence in the global car and truck market, however, continued to run into trouble in the United States.

Toyota, now one of the biggest producers in the world, had car and truck sales slip 12 per cent in July. That represented the 10th month in the past 12 in which Toyota posted a sales decline compared to the same month one year earlier.

Even Honda, which had been enjoying sales gains as consumers snapped up its fuel-friendly offerings, said the number of cars and trucks it pushed out the door shrank by 1.6 per cent.

Honda's car sales were up a healthy 14 per cent. But, as with the American automakers, the SUV and light truck side of the business took a hit in the month as sales fell 22 per cent.

The Canadian subsidiaries of all of the Japanese carmakers posted radically better results than did their parent companies in the United States.

On this side of the border, Toyota Canada grew sales by 18 per cent in July, thanks to strong sales of its Lexus cars and trucks.

Honda Canada experienced a 17 per cent spike in sales in this country. Here, its Acura and Honda divisions led the way in terms of sales.

And finally Nissan, which achieved flat sales in the United States, saw its Canadian numbers jump by 27 per cent.