DETROIT — General Motors reported its seventh consecutive quarterly profit on Wednesday but stressed the need for more cost cutting as profit margins declined. It also warned of a more difficult end to the year than Wall Street was anticipating.

G.M. said its third-quarter profit fell 12 percent, to $1.73 billion, or $1.03 a share, largely because of higher marketing and engineering costs. Revenue increased 8 percent, to $36.72 billion, but was down about $200 a vehicle, according to The New York Times.

Its chief executive, Daniel F. Akerson, declared the performance “not good enough.” The results compared with $1.96 billion, or $1.20 a share, in the period a year earlier.

The company earned $2.2 billion in North America but lost money in Europe, South America and its “international” division, excluding China, even though sales increased in every region and 9 percent over all. Executives said the carmaker would fall short of its goal to break even this year in Europe, before taxes and restructuring costs, as economic conditions there worsen.

Globally, G.M. said, fourth-quarter profits will be roughly the same as a year ago, which analysts said would translate to more than 40 percent below their estimates.

G.M. shares, already down 39 percent for the year, tumbled 10.9 percent, to $22.31, on Wednesday after the results were released. The drop has delayed the federal government’s plans to sell the 500 million G.M. shares it still owns, allowing the shadow of taxpayer ownership to linger over the company as executives work to make progress in its turnaround. The shares amount to a 26 percent stake.

“G.M. delivered a solid quarter thanks to our leadership positions in North America and China, where we have grown both sales and market share this year,” Mr. Akerson said in a statement. “But solid isn’t good enough, even in a tough economy. Our overall results underscore the work we have to do to leverage our scale and further improve our margins everywhere we do business.”

Rebecca Lindland, an analyst with the research firm IHS Automotive, said G.M. still needs to pare expenses to be successful long term but can only go so far in areas like product development.

“Toyota and Honda products are suffering right now because they were designed under tremendous cost pressure and it shows in cheap interiors and disappointing product reviews,” said Ms. Lindland, who is based in Greenwich, Conn. “G.M. simply cannot afford to sacrifice product for pennies. They must continue to build products that consumers are willing to pay for, and that’s much more likely to require significant investment.”

G.M., which went through bankruptcy protection in 2009 and executed the nation’s largest public stock offering nearly a year ago, has earned $7.1 billion through the first nine months of 2011. Its profit for all of 2010 was $4.7 billion.

On a conference call with analysts and reporters, Mr. Akerson said the losses in Europe and South America were “not sustainable and not acceptable.” G.M. this week appointed a new European president, Karl-Friedrich Stracke, and assigned him the task of speeding the division’s reorganization.

G.M. lost $292 million in the third quarter in Europe, about half as much as a year ago, but it had been profitable there in the second quarter and will continue to lose money there in the current quarter, G.M.’s chief financial officer, Daniel Ammann, said. He declined to say specifically how G.M. would address the situation, with actions like closing factories or cutting large numbers of jobs in Europe.

“There’s nothing that’s off the table,” Mr. Ammann said on a conference call later Wednesday.

Meanwhile, North America, the source of its biggest troubles before bankruptcy, has become its strongest asset, with pretax profits totaling $7.3 billion so far this year, even as sales shift toward small cars that cost less than the trucks and sport utility vehicles that were the lifeblood of the old G.M.

“Clearly, customers are seeing value in the vehicles we’re putting into the marketplace,” Mr. Ammann said. “Our margins aren’t where we want them to be, but we have a pretty clear road map, and we understand where the gaps are.”

In September, G.M.’s 48,500 hourly workers ratified a new four-year labor agreement that gave them bonuses of $5,000 but no wage increases except for those on the entry-level pay scale. G.M. said the deal, which calls for creating or retaining 6,400 jobs and moving some work to the United States from Mexico, increases the company’s labor costs by only about 1 percent a year.

G.M. was the most profitable of the three Detroit automakers in the third quarter. The Ford Motor Company earned $1.6 billion, and Chrysler earned $212 million.