For the month, Toyota was edged out as the number two US auto seller by Ford, whose US sales fell 8.1 percent. Chrysler's US sales dropped 1.8 percent, while Nissan's rose 22.7 percent and Honda Motor Co. rose 11.5 percent, the automakers said.
GM said it sold 320,668 passenger vehicles in June, compared with 407,513 during the same period last year. The declines for GM and Ford came as they continued to wean themselves from low-profit sales to rental car companies.
Paul Ballew, GM's executive director of global market and industry analysis, blamed the company's sales decline on a planned reduction in fleet sales and a tough comparison with June of last year, when the company offered a big 72-hour sale.
Also, he said GM was surprised that Toyota offered zero-percent financing for 60 months, which cut into GM's pickup truck sales. He said the company may wind up altering its strategy of offering fewer incentives on pickups.
"If we have to make some changes in our incentive play, we will, because we are not going to cede ground in a category that we feel we're best in class in," he said.
GM's top-selling pickups, the Chevrolet Silverado and GMC Sierra, saw declines of more than 20 percent, while Toyota Tundra sales more than doubled.
Toyota said it sold 245,739 Toyota and Lexus vehicles in June, compared with 223,018 a year ago. For the first half of the year, it sold 725,219 vehicles.
Toyota-brand passenger cars recorded best-ever June sales of 128,239, an 8.9 percent increase over the same period last year. It was led by the Camry, with June sales of 46,630, up 12.5 percent over the same period last year.
Industrywide US sales in June fell 3 percent to 1.4 million from 1.5 million in 2006, according to Autodata Corp. For the first half of the year, sales dropped 1.5 percent to 8.2 million from 8.4 million during the year-ago period.