Tyson was arrested in December 2006 in Arizona

He was arrested in December 2006 in Arizona after being spotted driving erratically as he left a nightclub.

Tyson, 41, initially denied the charges at an earlier hearing in January.

Tyson served three years in prison after a conviction for rape in 1992 and was jailed again in 1999 for assaulting two people after a traffic accident.

The latest charges carry a total maximum sentence of just over four years in jail.

Rehab

He was arrested in Scottsdale, Arizona on 29 December after nearly crashing his car into a police car as he left a nightclub.

Prosecutors said Tyson had 2.16g of cocaine in his possession and traces of marijuana in his system when he was arrested.

At the time of his arrest, police reportedly said the former boxer admitted that he was addicted to cocaine.

At the plea hearing Tyson's lawyer, David Chesnoff, said the former champion was undergoing rehabilitation treatment in California and has been clean for eight months.

"He took the bull by the horns and has managed to deal with his addictions and stay sober for an extended period of time," Mr Chesnoff told reporters after the hearing.

"He's not in denial. He's acknowledged that what he did was wrong," he added.

In 1986 Tyson became the youngest heavyweight champion in history, aged 20.