Anthony Joshua's promoter Eddie Hearn has expressed caution over an offer of 50 million US dollars from rival champion Deontay Wilder for a world heavyweight title unification fight.
Wilder, who holds the WBC version of the title, made the unusual move of emailing Joshua directly to insist his backers had the money - worth £35.9million - for the bout which could take place later this year.
Hearn explained that he still required plenty of assurances before committing to any deal, and said talks that he expected to happen with Wilder's representatives in New York on Thursday were called off.
But Hearn added that he was optimistic a deal to make the biggest bout in the division was drawing closer.
Hearn told Sky Sports News: "We were supposed to meet today with (Wilder's promoter) Shelly Finkel and (manager) Al Haymon. They cancelled that meeting, which was disappointing. I've requested a meeting for tomorrow. We'll see if we can get on that one.
"There is no deal - there's no contract, there's no serious offer. We have to determine if it is a PR move or a genuine offer.
"For a fighter to send another fighter an email telling them they've got this money is very strange, but it is a wonderful PR move.
"I think it's bringing the fight closer. From our side absolutely no doubt this is the fight that Anthony Joshua wants next. I believe Deontay Wilder wants this fight next so that's always a great move."
Joshua added the WBO title to the IBF and WBA belts he already owned when he dispatched Joseph Parker in a gruelling contest in Cardiff last month.
Meanwhile Wilder extended his professional record to 40 straight wins when he produced a superb 10th-round knockout over Luis Ortiz to retain his own title last month.
Wilder has reportedly agreed to make the next defence of his WBC crown against fellow American Dominic Breazeale, whom Joshua dispatched with ease in an IBF title defence two years ago.
But Hearn is clearly determined that if a deal between Joshua and Wilder can be done, the unification contest should take place sooner rather than later.
Hearn added: "This is the fight that boxing needs: an undisputed heavyweight championship of the world must be made. Let's forget 'after', let's do it now."