NEW YORK (Reuters) - Donald Trump has turned down an offer to drive the pace car at the Indianapolis 500 because it would be "inappropriate" while he considers a possible 2012 run for the Republican presidential nomination, race organizers said on Thursday.

The Indianapolis Motor Speedway had selected the U.S. real estate mogul and reality TV star to be the celebrity pace driver for the race on May 29, but a busy schedule has left Trump unavailable.

"I very much appreciate the honor but time and business constraints make my appearance there, especially with the necessary practice sessions, impossible to fulfill," Trump said in a statement released by the Speedway. "I look forward to watching the race from New York."

According to race organizers, Trump told them he may soon be announcing his intention to run for the Republican presidential nomination and thought it would be "inappropriate" to drive the pace car.

His withdrawal comes as a "Dump Trump" campaign to have him removed as pace car driver picked up speed with race fans angered that someone with no connection to racing would get the honor on the event's 100th anniversary.

A replacement for Trump has not been named for the event widely known as the "Greatest Spectacle in Racing."

(Writing by Steve Keating in Toronto; Editing by Frank Pingue;