Nissan Motor Co. is growing faster in the U.S. than any mass-market carmaker and edged past rival Honda Motor Co. in this year’s first half. That might not be a good thing for Nissan’s bottom line.

Chief Executive Officer Carlos Ghosn wants Nissan to pass Honda and get 10 percent of the North American market. Yet Nissan’s growth this year has been helped by more generous incentives to customers and by selling more low-margin vehicles to rental fleets, which have risen faster than any other automaker’s.

Ghosn’s push for sales risks delivering growth at the expense of margins. It also underscores the fact that U.S. market expansion is slowing and another record year is looking less likely. So growth-hungry companies like Nissan may need to spend more to boost sales.

“They’re going at it at all costs,” said Jessica Caldwell, an analyst at car-pricing website Edmunds.com. “To get 10 percent, Nissan is really chasing sales volume over margins.”

Nissan isn’t doing it all with low-priced sales. The new Maxima sedan and Rogue sport utility vehicle have been hits. In the second half of the year, the company will increase production of its new Titan pickup truck and Armada full-size SUV to boost deliveries, said Judy Wheeler, vice president of U.S. for Nissan.

In the first half, Nissan sold almost 800,000 vehicles in the U.S., beating Honda by about 6,000 and pushing its own market share to 9.2 percent from 8.6 percent in the same period last year, according to Autodata Inc. Nissan now has 9.7 percent market share in North America.