Carter said he expects to increase Toyota's share later this year because it is increasing production of Prius hybrids and Camrys. In April, he said, the company could have sold more of the cars if it had them. It also has a new sports car, the Scion FR-S, and a redesigned Avalon sedan going on sale.
Johnson, GM's U.S. sales chief, noted that Japanese automakers are also being aggressive in the rental-car market, which GM is trying to pull out of because it's less profitable.
Johnson said a 25-percent drop in rental fleet sales was partly to blame for GM's 8-percent sales decline in April. Buick, Cadillac and Chevy sales were down. Only GMC had an increase, and it was small at 4.5 percent.
Sales of the Chevrolet Cruze compact fell almost 28 percent to just over 18,000 as it faced growing competition from Ford, Hyundai and others. The Cruze has been a star for GM for more than a year, and April of 2011 was among its strongest months.
GM made up for some of that loss with strong sales of the new Sonic subcompact, which handily beat the Toyota Yaris and Ford Fiesta.
Plummeting Fiesta sales were among the reasons for Ford's 5-percent decline in April. Fiesta was down 44 percent, as buyers increasingly moved up to the larger Focus. The Fiesta is also facing new competition from the Prius C.
Other Japanese automakers didn't fare as well as Toyota. Nissan's sales were flat compared with last year. Sales of the all-electric Nissan Leaf fell 35 percent even though the car is at more dealerships than it was last year.
Honda said sales fell 2 percent. Strong demand for the new CR-V crossover and the Accord sedan were unable to make up for sliding sales of the Civic.
Jesse Toprak, vice president of market intelligence for the auto information site TrueCar.com, said Honda lost market share in April even though it spent an estimated $500 more per vehicle on incentives than Toyota. TrueCar estimated that Honda spent just below the industry average of $2,446 per vehicle, which was up 6 percent from last April. GM spent the most, at $3,156.
Other automakers reporting Tuesday:
— Chrysler sales jumped 20 percent, with the Ram pickup posting a 19-percent gain. Chrysler was also helped at the smaller end of the lineup, where Fiat 500 small cars sold four times as many as they did last April. But KBB.com noted that Chrysler is offering $3,000 incentives on the Chrysler 200 and Dodge Avenger, and said the company is relying too heavily on deals to drive sales.
— Volkswagen of America Inc. said its sales rose 31.5 percent in April, helped by sales of its redesigned Passat and Beetle models.
— Hyundai said its sales rose 1 percent, led by the new Accent and Veloster small cars. Hyundai also saw a 36-percent increase in sales of its luxury Genesis and Equus models.