Mike Tyson's manager Shelley Finkel has warned Lennox Lewis that he will price himself out of the long-awaited world heavyweight title fight between present and former champions if Lewis continues to insist that he is paid 75% of whatever purse money is available.

"If the offer to us is only 25%, then it is not happening," said Finkel after Tyson bowed to pressure from the Lewis camp to cancel an interim bout against the veteran Ray Mercer in Atlantic City on January 19 and move instead towards a Lewis fight on April 6.

Lewis, who successfully secured his rematch against Hasim Rahman after resorting to legal action, had begun proceedings in a Manhattan Federal Court to force Tyson to face him instead of Mercer, and Tyson's advisers recognise the probability of the court ruling in Lewis' favour once again by agreeing to abandon plans for the Mercer fight. Now weeks of intensive negotiations will begin.

Firstly rival promoters must reach agreement. Lewis has taken control of his own career by setting up Lion Promotions, who will work in conjunction with the champion's long-time American promoters Main Events. Meanwhile Tyson is represented by America Presents, headed by the television executive Matt Tinley. Together the promoters must negotiate the most lucrative site for the contest to take place. Traditionalists might welcome the possibility of New York's Madison Square Garden but the probability is that one of the huge Las Vegas casino and hotel complexes will provide the financial guarantees to prevail.

Las Vegas has been badly hit by the decline in the American tourism industry in the wake of the New York terrorist attack, with room occupancy rates falling dramatically, and the casinos are keen to ensure that the attraction of the biggest fight of the year is not lost.

The rival television companies HBO, who have Lewis under contract, and Showtime, with whom Tyson has a long-term agreement, have agreed in principle to work together on a major promotion for the first time. But details of the arrangements, not least the mechanics of the pay-per-view, are some way from being finalised.

Suggestions have been made that Lewis-Tyson might generate in excess of $100m, which could be fanciful thinking, but the fight would be the biggest since June 28 1997 when Tyson and Evander Holyfield were each paid $30m for their second meeting which Holyfield won when Tyson was disqualified for biting.

Lewis is the title-holder for the World Boxing Council, International Boxing Federation and International Boxing Organisation, with the WBC being generally recognised as the governing body with the most highly valued belt.