General Motors Co. tripled its profit in the first quarter, helped by stronger demand but mostly because the auto maker made money off the sale of its stakes in two former subsidiaries.

Without those asset sales, GM's earnings disappointed investors and highlighted difficulties in its core North American operations and other units around the world, reported The Wall Street Journal.

GM's income rose to $3.2 billion, or $1.77 a share, from $865 million or 55 cents a share, lifted by $1.5 billion in gains on sale of holdings in Delphi Automotive LLP and Ally Financial. Without those gains, its earnings before interest and taxes rose 18 percent to $2 billion, and North American profit climbed just 8 percent to $1.3 billion, less than analysts had expected. Revenue increased 15 percent, to $36.2 billion, from $31.5 billion.

"We are making steady progress, but there is more work to do," Chairman and Chief Executive Daniel Akerson said on a conference call Thursday.

The auto maker expressed optimism about the rest of 2011, saying it expects a rise in operating profit for the full year. A gain would build on the $4.7 billion that GM made in 2010, its most profitable year since 1999.

Mr. Akerson, however, said "intensive cost cutting" is essential to ensure the future profit growth as rising commodity costs push up the prices GM is paying for finished parts and materials. The company also plans to pare incentive spending for the rest of the year. High discounts early in the year were one of the problems that hurt its North American profits.

Chief Financial Officer, Daniel Ammann, said GM's forecast factors in high fuel prices, now at more than $4 a gallon in most of the United States. High gas prices tend to drive down sales of high-margin pickup trucks and sport-utility vehicles.

Even though consumers are downsizing their purchases, he said, many are opting for smaller SUVs, rather than cars, and those who are switching to cars are paying more for them. "It isn't all about people moving from large SUVs into cars," Mr. Ammann said.

In North America, GM had the benefit of rising demand. Truck production in the first quarter increased 18 percent, and car production 16 percent. Higher production lifts revenues because auto companies book revenue when a vehicle leaves the factory.

But steep discounts offered in January and February eroded its margins. Lower pricing cut its operating profit by $300 million, the company said. Including its special gains, GM's profit per vehicle in North America was $3,687; without them, it made just $1,653 per vehicle. Ford Motor Co. made about $2,806 a vehicle in North America in the first quarter.

GM shares were off 2.3 percent, or 77 cents, to $32.27 in recent New York Stock Exchange trading.

"A decent quarter but short of the upside we were looking for," Citibank analyst Itay Michaeli said in a note.