The decision is likely to now face legal action from Klitschko's camp. As the number one contender for the title it was expected the fight would take place in April.
But now it seems the lure of one final massive pay-out for the 37-year-old boxing champion has been enough to replace Klitschko with Tyson - a fight likely to take place in Memphis in June.
Said Universum Box-Promotion chief Klaus-Peter Kohl: "Lennox Lewis is no longer ready to fight Klitschko as had been agreed.
"I must clearly say that I regard this as a breach of contract.
"I will hold talks over the next few days and study all options regarding possible legal action."
The staging of sporting events is just one of the topics to be discussed at SportAccord, the leading industry conference taking place in Madrid between May 12-16.
To find out how YOU can attend, click on the link below to visit the official SportAccord website.
