DETROIT - U.S. sales for German luxury automaker Audi will increase to at least 90,000 this year, and would be 5-7 percent higher than that if it had more cars to sell, Audi of America President Johan de Nysschen said.

Audi, the best-performing premium brand in the U.S. market so far this year, is constrained by lack of vehicles in U.S. showrooms with just 33 days of supply -- compared with the 60 days it normally carries -- De Nysschen told reporters after a speech to the Automobile Press Association.

De Nysschen said his estimate for 2010 U.S. sales is conservative, noting that the company's U.S. sales in the first quarter of 21,315 units was a record and up 35 percent from the first quarter in 2009.

Audi U.S. sales would increase about 9 percent if it sold 90,000 units this year.

Audi's vehicles sold in the United States are made in Europe. Audi increased the allocation to the U.S.-bound vehicles by 3,000 units for 2010, which still won't be enough to match demand, de Nysschen said.

"In America, we are experiencing what you'd call an enviable problem: we're constrained by supply," de Nysschen said. "We have been running short since around August of last year."

About 30 percent of Audi's U.S. sales come from pre-orders: customers signing to buy before vehicles arrive at dealers.