INDIANAPOLIS (AP) - The U.S. Grand Prix won't return to the Indianapolis Motor Speedway next year, and it's unclear if the Formula One race will remain in the United States.

The race will not be held at Indy in 2008 after eight years at the track, spokesman Ron Green said Thursday. He declined to give other details, but said speedway CEO Tony George would hold a news conference later in the day.

George had set Thursday as the deadline for reaching an agreement to extend the contract with F1. Indianapolis, the only American race on the F1 schedule, draws one of the biggest crowds on the circuit.

George, who met with F1 boss Bernie Ecclestone last month during U.S. Grand Prix weekend in Indianapolis, had said he was confident a new deal would be reached.

But Ecclestone had repeatedly said F1 did not need to race in the United States, while also mentioning the possibility of moving the U.S. Grand Prix to New York or Las Vegas.

The 4.18-kilometer (2.6-mile), 13-turn road course was built inside the speedway's famous oval to attract the F1 race.

Attendance figures are not released at Indianapolis, but estimates have been around 125,000 each of the past six years. The inaugural race in 2000 drew more than 200,000.

The event was marred in 2005 when 14 of the 20 drivers pulled off the track just before the start over concerns about the safety of the Michelin tires used by seven teams. Afterward, George refused to wave the checkered flag or join Michael Schumacher in the winner's circle.

Last year's negotiations to extend the deal dragged into August before the two sides agreed to a one-year deal. Speedway officials had said they wanted a more permanent solution this time.

Despite F1's absence, the speedway could still be the site of three races next year as track officials expect to announce with MotoGP, the international motorcycle racing series, next week.

Besides the Indianapolis 500, the speedway also is the site of NASCAR's Allstate 400 at the Brickyard on July 29.