DETROIT — Auto sales were expected to rise only slightly in July, adding to concerns in the industry that Americans are pulling back on car buying.

Analysts predicted a small increase in U.S. sales of new cars and trucks. A lack of discounts and lingering shortages of Japanese cars kept many buyers away. Americans also worried about the economy.

“There’s definitely some weakness kind of looming out there,” said Jeff Schuster, executive director of global forecasting at J.D. Power and Associates.

Sales started strong this year, but have slowed as the economy’s growth faltered and Japan’s earthquake caused shortages of popular models sold by Honda and Toyota. The unemployment rate rose to 9.2 percent earlier this summer, the highest level this year, and consumer confidence is shaky.

But July wasn’t a total loss. Sales of compact cars and newer, more fuel-efficient SUVs rose.

Trucks sales were down, however, hurt by continuing weakness in construction.

Sales rose 8 percent at General Motors, led by fuel-efficient vehicles such as the Chevrolet Cruze, which can get 30 mpg in combined city-highway driving. Sales rose sharply for the Chevrolet Equinox and GMC Terrain small crossovers, which also get good gas mileage.

GM Vice President of Sales Don Johnson said many customers decided to hold off buying cars because wrangling over raising the government’s debt ceiling made buyers nervous.

“Uncertainty … is always bad for consumers,” Johnson said.

Ford Motor Co. said sales rose 6 percent. The new Explorer saw sales more than double a year ago. The Fiesta saw sales rise 58 percent. But the popular Focus couldn’t capitalize on strong small-car sales because problems at a factory limited production.