INDIANAPOLIS -- Tony Stewart passed up a chance to race for Roger Penske in the Indianapolis 500.

The three-time NASCAR champion said Wednesday at the International Motorsports Industry Show that he wouldn't attempt to race in both the Indy 500 and NASCAR's Coca-Cola 600 on the same day.

"As much as I would like to do it, we just don't have the time to do it proper," Stewart said. "The IRL is so competitive now, you're not going to just show up like drivers used to do in the past and be competitive. These guys don't leave anything on the table there. You're not going to stroll into the Indy 500 with these guys who race every week and be as competitive as they are."

Penske extended the invitation last week in Las Vegas while accepting the Sprint Cup trophy. Later, when given the chance to shrug it off as a lighthearted moment with Stewart, Penske insisted he was very serious about fielding a car for the NASCAR owner-driver.

There was a push to get Stewart to race in Indianapolis since Penske made the offer, with Indianapolis Motor Speedway starting an online petition for fans to encourage the driver to accept the ride.

Stewart has raced five times in the Indy 500, starting from the pole as a rookie in 1996 and leading 44 laps before his engine failed. His highest finish was fifth in 1997.

The Indiana native twice ran both the Indy 500 and Coca-Cola 600 on the same day. In 1999, he was ninth at Indy and fourth at Charlotte, and in 2001, he was sixth at Indy and third at Charlotte.

Penske-owned cars have won the Indianapolis 500 15 times.

Brad Keselowski, the NASCAR Sprint Cup champion for Penske, said he'd like to try a double himself.

"Tony's a Chevy driver. If Ford had an IndyCar presence, I hope Roger would talk to me," Keselowski tweeted. "Who wouldn't want to do it?"

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