The 70-year-old Simpson, acquitted in a sensational double-murder trial that gripped America two decades ago, appeared before a state parole board by live video feed from Lovelock Correctional Centre, about 161 kilometres from the parole board's office in Carson City.

"I've done my time, I've done it as well and respectfully as anyone can," Simpson told the board members. "None of this would have happened if I'd had better judgment."

After his conviction in 2008, a judge sentenced Simpson to nine to 33 years in state prison, meaning that he becomes eligible for parole for the first time October 1. Based on his age and the fact that he has been a model prisoner, the Nevada Board of Parole Commissioners granted his release the first time it was considered, rather than denying parole and making him wait years for another chance.

The board listened to Simpson and others for more than an hour and made the decision in about 30 minutes. It normally takes days to render a decision, but it announced its ruling on the same day in light of the high-profile nature of Simpson's case.

He was joined by supporters including his daughter, sister and one of his robbery victims.

Exactly 13 years after his 1995 acquittal for the murders, Simpson was found guilty of storming into a Las Vegas hotel room with four others to retrieve at gunpoint items that he claimed were rightfully his from two sports collectibles dealers.

Under questioning by parole commissioners, Simpson stuck to a version of the robbery that, as the board member Tony Corda said, "differs a little from the official record".

He insisted that the items he took from the memorabilia dealer, Bruce Fromong, whom he knew well, were his property. And he said he was not aware at the time that two of the men he took to the hotel room, whom he referred to as "security guys," brandished guns.

He said he had never brandished a weapon at anyone, and never would, adding, "I basically have spent a conflict-free life."

The board said it had received hundreds of letters in support of, and opposing, Simpson's parole. It said those against his parole asked it to consider charges that Simpson killed his wife Nicole and her friend Ronald Goldman in 1994 and a subsequent civil judgment against Simpson.

The board said it would not take into account his 1995 acquittal or the civil court decision that found him liable for the deaths and ordered him to pay $US33.5 million in damages to the victims' families, a judgment that has gone largely unpaid.

The same board delivered Simpson a favourable parole ruling in 2013 on some of the robbery-related charges, leaving him with four years to go on his minimum sentence. A similar decision this time would clear the way for Simpson to walk out of prison on October 1.

The board could require him to go to a halfway house, or impose other terms. If he violates those terms, he could return to prison and serve up to the full 33-year sentence, minus time credited for good conduct.

Simpson won the Heisman Trophy, the award for the top college football player, in 1968 while attending the University of Southern California. He played more than a decade in the National Football League, becoming the first player to rush for more than 2000 yards in a season.

Following his playing career, Simpson became known for his work as a pitchman in television commercials for companies like Hertz and for roles in movies like the comedy The Naked Gun. 

Reuters, New York Times