BMW (BMWG.DE), the world's largest premium carmaker, expects to post U.S. sales growth in the last four months of 2009 as the economy shows signs of coming out of the worst part of the recession, the head of its U.S. operations said on Tuesday.

BMW North America President Jim O'Donnell told Reuters in an interview that the company expects to sell about 17,500 vehicles in the United States in September, 3,000 more vehicles than a year ago.

I think car sales will continue to steadily rise as we move out of the worst of the recession, O'Donnell said.

September through December, I believe we'll be up in that four-month period, he said.

BMW's U.S. sales fell 18 percent to 24,343 units in August. Through the first eight months of 2009, BMW's sales in the United States, its largest single market that accounts for 20 percent of its global sales, fell 26 percent to 160,044 units.

The overall U.S. market is down about 30 percent over the same period.

Industry-wide auto sales boomed in August as consumers burned through $3 billion in the Cash for Clunkers incentives that offered up to $4,500 for consumers trading in old gas guzzlers for new, fuel-efficient ones.

O'Donnell said BMW Group sold about 2,000 vehicles under the Clunkers program in August, 1,600 for its MINI brand and 400 for its BMW brand.

The fascinating thing to me about the whole Cash for Clunkers program is the way that the government can motivate people to go out and buy cars that the manufacturers single-handedly failed to do, O'Donnell said.

He forecast mass-market manufacturers would see a decline in sales in September, but said BMW and other premium brands would see little impact from the end of the program, partly because the Clunkers rebates were limited to cars priced under $40,000.

U.S. industry sales are expected to increase to 11.5 million units in 2010, up from some 10 million units projected for this year, he said.

I think the worst is over, O'Donnell said. Next year, we can look forward to some sort of growth in the marketplace. I don't know whether it's going to be 10 percent or 20 percent, but somewhere between that.

(Reporting by Soyoung Kim; Editing Bernard Orr)