NEW YORK (CNN/Money) - The Big Three automakers Tuesday reported a drop in U.S. sales in June, as attractive incentives failed to keep sales at year-earlier levels.

General Motors Corp. and Chrysler Group stressed that fewer selling days during the recent month left the daily sales rates higher than year-earlier levels. And all three automakers said they expect to see improved auto sales in the second half of 2003.

CNNfn's Mary Snow takes a look at June auto sales and the effect rebates have had on these numbers. Play video (Real or Windows Media)

GM (GM: down $0.33 to $35.67, Research, Estimates), the world's largest automaker, sold 425,975 cars and light trucks in the month, down from 455,628 a year earlier. But the automaker said that the most recent month had 24 selling days, compared with 26 a year ago, so it said the sales rate increased 1.3 percent from a year ago.

Even with that adjustment, the sales rate for GM cars fell 8.5 percent, but that was balanced out by a 10.1 percent increase in the sales rate for light trucks, such as pickups, sport/utility vehicles and vans, which also showed a slight increase in total sales.

"Despite some economic uncertainty, industry sales levels for the first half of the year have been in line with our expectations," said a statement from GM Group Vice President John Smith. "We remain optimistic that the second half of the year will improve and that this momentum will carry into 2004."

But Paul Ballew, GM's executive director for market and industry analysis, warned analysts that the company would see a sharp drop in fleet sales to businesses, primarily car rental companies, in July and August, compared with earlier expectations. He said most of those sales have been delayed to the later in the year rather than canceled.

Ford (F: down $0.15 to $10.84, Research, Estimates) said new U.S. vehicle sales declined 7.7 percent in the month compared with a year earlier, leaving it down 3.0 percent for the first six months of the year. Light trucks were off 4.1 percent, while car sales dropped 13.7 percent. The overall daily sales rate would have been off 0.03 percent using GM's method of calculating sales gain.

"We don't subscribe to that adjustment even when it works out in our favor," George Pipas, Ford's manager of sales analysis, told analysts and reporters Tuesday.

Pipas said that sales for both Ford and the industry were a bit below Ford's expectations, given its reading of May sales and the fact that incentives to auto buyers stayed at the same high level in June. But he said that Ford expects the industry to see improved second-half sales, citing the impact of the recent tax cut, lower interest rates that the company expects will support stronger economic growth, and the end of some of the uncertainty in the first half.

Chrysler Group, the key North American unit of No. 3 automaker DaimlerChrysler (DCX: down $0.03 to $34.69, Research, Estimates), saw its daily sales rate up 6 percent, although its overall number of vehicles sold slipped 2 percent to 198,962.

The company saw its overall car sales fall 6 percent, as the car sales rate edged up 1 percent. Light trucks, which account for more than three-quarters of its overall sales, saw the sales rate climb 8 percent, while total sales slipped 0.4 percent due to weak sales of minivans.

Among overseas automakers, Toyota Motor Corp. (TM: up $0.43 to $52.23, Research, Estimates) reported a rise in overall sales as well as sales rate in June. The nation's No. 4 automaker saw the sales rate rise 10.9 percent, as the overall sales rose 2.4 percent to 155,501.