Sales have continued their downward slide at US carmakers General Motors (GM) and Ford.
US carmakers are paying out more on incentives to lure buyers
GM sales sank 14% in March to 365,375 vehicles compared with a year earlier, while Ford's overall sales fell 4.6%.
But the last of America's Big Three carmakers, DaimlerChrysler's Chrysler unit, racked up a 2% rise in sales.
The figures were in direct contrast to those of Asian rival Toyota which has been steadily raising its market share - Toyota's sales rose a record 7%.
The Japanese car firm thanked sales of new vehicles such as the Rav4 and FJ Cruiser SUVs, as well as the redesigned Camry and the new Yaris subcompact, for the increase.
Among other Asian car firm's Honda sales rose just 0.2% during the month and Hyundai's were up 4.3%.
However, Nissan's US motor sales fell 2.6% during the period.
The fall was not as large as that suffered by US giants Ford and GM as they battle to shake-up their businesses.
Both firms have unveiled plans to cut workers and close down factories in an effort to make their businesses more competitive.
"We're not there yet, but we are reducing the rate of decline and that's our goal in 2006," Ford's chief sales analyst George Pipas said.
However, efforts to stem the slide in sales have come at a price according to research.
In an effort to lure buyers, car makers have been offering discounts and other incentives on their vehicles.
A survey released by industry tracking firm Edmunds.com said the average incentive on a vehicle sold in March had risen 7% to $2,510 compared with a month earlier.
The industry spent an estimated $3.8bn on such offers - with GM and Ford accounting for approximately 71% of the total, the survey added.