Former heavyweight boxing champion Evander Holyfield may be 40 years old but he vowed on Tuesday to keep fighting until he regains his crown.

His next opponent, International Boxing Federation (IBF) World Cruiserweight champion James Toney believes the end may be near for Holyfield, the only heavyweight in history to win a world titles on four separate occasions.

"This will be your last fight," Toney told Holyfield during a news conference here promoting their bout at the Mandalay Bay Resort and Casino in Las Vegas on October 4.

Holyfield failed to impress in his last fight, losing on points to Chris Byrd for the then-vacant IBF version of the heavyweight championship in December 2002.

He faced questioning about when he might decide to finally decide to end a career that began at the age of just eight when he entered a Pee Wee tournament.

"The end is when I'm undisputed champion of the world and I can't put that into a timeframe," Holyfield told reporters.

To fulfil his dream, Holyfield must first secure a fight against one of the current champions.

Britain's Lennox Lewis currently holds the World Boxing Council's version of the title, Roy Jones Jr. is the World Boxing Association champion and recent opponent Chris Byrd holds the IBF crown.

Holyfield said his box-office appeal should ensure he got another title shot.

"People like making money and when I fight people come to watch and the only way you can make money is people watching.

"I'm sure neither one of the champions want to fight me but because the big payday is there they will come along," the former champion told reporters.

Toney, 34, will be fighting as a heavyweight for the first time. He picked up IBF cruiserweight crown with a points victory over champion Vassiliy Jirov in April this year.

He was asked by reporters about how he would prepare for the step-up in weight.

"I'm going to eat a lot more," the Grand Rapids, Michigan native said.