Foreman has not fought since losing to Briggs in 1997

King said he talked with the 55-year-old former heavyweight champion about the prospects of a $20m fight.

"We've got a verbal deal," King said. "(Foreman) said, 'I'm willing to fight one more time.'"

Foreman has not fought since 1997, when he lost his heavyweight title to Shannon Briggs.

Since then he has worked as a boxing commentator and concentrated on his burgeoning business interests.

"George said he wants to come back to fight again, so what I'm doing is calling him out," King said. "He has the power, boy, he's rewriting history books."

King said no opponent, date or location have been set, although Foreman said last week he would like any fight to be in his hometown of Houston.

Moorer victory

Foreman first won the heavyweight title in 1973 by knocking out Joe Frazier.

He lost the title the next year to Ali in a bout in Zaire known as the Rumble in Jungle. That fight was the first professional championship bout King promoted.

In 1987, after a 10-year retirement, Foreman made his first comeback.

Seven years later, at 45, Foreman marked the 20th anniversary of the Ali fight by knocking out Michael Moorer to become the oldest man to win the title.