Two-times Indianapolis 500 champion Al Unser Jr will miss at least the next two Indy Racing League events while he is treated for alcohol abuse.

Unser revealed he would be receiving treatment hours after prosecutors said he would not face criminal charges over accusations that he hit his girlfriend and left her stranded on a road.

"I have a problem with alcohol abuse," said Unser.

"Nearly every poor choice that I have made in my life was under the influence of alcohol.

Violent argument

"I don't understand why I have a problem, but I know I have to straighten out."

Unser's girlfriend, Jena L Soto, told police on 9 July that she and Unser hit each other during an argument while she was driving him home from a strip club.

Soto cooperated with the police but repeatedly told them she did not want to press charges.

"I made some very poor choices and spent the night in jail," said Unser.

"That is something that I want to never do again."

'Hit in the face'

In her emergency calls and statements, Soto said that she was driving to Unser's motor home at the Speedway because he was intoxicated.

She told officers she hit Unser first to stop him from trying to shift the gears of the vehicle, and that Unser responded by hitting her in the face.

She said she pulled to the side of the highway after Unser hit her, got out of the sport utility vehicle, and that Unser then drove away.

Marion County Prosecutor Scott Newman said he could not have filed drunken driving charges against Unser even though evidence suggested that he was drunk.

Legendary status

Newman said that no one had seen Unser driving in an impaired state and officers did not obtain a blood-alcohol test.

Unser is a member of a family that has attained legendary status in American motor racing.

His father Al and uncle Bobby were champions, and Al Jr inherited the family talent.

He was a front-running driver in the Cart series throughout the 1980s and early 1990s, winning the title twice.

But his form dropped off in the mid-1990s and he was forced to switch to the rival Indy Racing League.

Unser has not been a consistent winner for seven years, but this season has been his best season in years - he is sixth in the IRL standings.