Small car sales have slowed, in part because gas prices are relatively low. AAA said the average price for gas fell in March for the first time in a decade, down 14 cents to $3.64 a gallon. Sales of Toyota's Prius hybrid dropped 23 percent in March.

But pickup trucks made up for that. GM, Ford and Chrysler sold a total of 154,722 full-size pickups, up 14 percent from a year ago. It's the third straight month that pickup sales have outpaced overall industry sales.

Pickup truck sales should keep increasing through this year and at least into early next year, said Jeff Schuster, senior vice president of forecasting for LMC Automotive, a Detroit-area forecasting firm.

Small businesses and the housing industry are recovering from the recession after a long lag. Oil production in the U.S. is higher than it's been in two decades. And automakers are offering big discounts on trucks. GM, for one, is trying to clear out older models before the debut of its 2014 pickups later this spring.

Car buying site Edmunds.com estimates that GM offered $5,800 in discounts on the Chevrolet Silverado in March, compared with $4,010 for its chief rival, Ford's F-150.

"I think the pickup truck battle is starting to heat up at the same time demand heats up," Schuster said.

On Tuesday, Edmunds.com raised its forecast for full-year U.S. sales to 15.5 million from 15.0 million. That's much healthier than the 10.4 million sold during the economic downturn in 2009, although still below the 17 million recorded in 2005. The industry sold 14.5 million cars and trucks last year.

Conditions look so good that some analysts think automakers will have to increase production and hire more workers to keep up.

Automakers have added 125,800 jobs since February of 2010. That's a nearly 20 percent increase in industry employment, according to the U.S. Department of Labor.

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