Tyson Fury v Dillian Whyte is unlikely to happen in March with the purse bids now set for Friday, according to Eddie Hearn.
Mandatory challenger Whyte has been unable to agree to terms with Fury after the WBC ordered an 80/20 purse split in favour of the reigning champion.
Speaking to the 5 Live Boxing podcast, Hearn said: "People keep talking about March dates - that's starting to look unrealistic for a fight of this magnitude."Listen: 5 Live Boxing with Steve Bunce
Fury's co-promoter Frank Warren told BBC Sport last week that the targeted date was 26 March, but Hearn says April is far more likely.
"Either March, April, early May potentially," added Hearn. "This is the window for the fight. Depends what happens this week.
"There are so many conversations going on behind the scenes right now. Something could turn at any moment."
Whyte, 33, is currently in a dispute with the sanctioning body WBC after their purse-split announcement and also the time it took for the British heavyweight to receive his shot at the world title.
Hearn, who works with Whyte, says despite the disagreements between the two camps and the WBC, the fight will still go ahead.
"You're talking about a lot of money - a difference of 25%," Hearn said about the issue.
"The normal split for any mandatory challenger is a lot more than 80/20. The normal split for an interim champion is up to 45%. We feel in terms of the commercial value of Dillian Whyte and the time he's had to wait, 80/20 is quite ridiculous really."
He added: "[It] looks like Dillian Whyte will definitely get his shot at the WBC title, but we have to fight for his rights and make sure it's fair. It's not going to stand in the way of the fight."
Usyk v Joshua II 'likely' in AprilAnthony Joshua was beaten on points by Oleksandr Usyk last September
Elsewhere in the heavyweight division, Hearn confirmed Anthony Joshua was expected to fight Oleksandr Usyk in April in their much-anticipated rematch.
Joshua is seeking to reclaim the heavyweight titles - WBA (Super), WBO and IBF - he lost to the Ukrainian in September.
Talks are ongoing, but promoter Hearn said it was likely the rematch would take place in the UK.
"It's a must win for Anthony Joshua. I'd love to see him get victory on UK soil," he said.
"April is the likely date for that. I feel it's a fight that will take place in the UK again. Spurs [Tottenham Hotspur stadium] would be a great place to revisit. Wembley also.
"Once you start getting into April, early May the weather gets a bit better. We've had a number of international offers."
Joshua has announced he will make changes to his training team, but there is yet to be any official word on what coaches could be drafted in and whether the two-time heavyweight champion intends to split with Rob McCracken.
"I don't see this as a clear out, getting rid of everybody. I feel it's a tweak," Hearn said about the upcoming announcement.
"He knows he must get this right. He's been doing the work behind the scenes making sure he builds the right environment and team."
Taylor v Serrano deal 'on the verge'Katie Taylor is the WBA, WBC, IBF, WBO, and The Ring lightweight champion
Irish boxer Katie Taylor is in line to finally fight seven-weight world champion Amanda Serrano in the United States in April.
Serrano has seen her profile soar in the US since teaming up with YouTuber turned boxer Jake Paul - and both women are considered among the greatest female fighters of all time.
Hearn - who promotes Taylor - revealed the agreement was "on the verge" of completion and he was targeting a 30 April fight date at the iconic venue of Madison Square Garden in New York.
"Taylor-Serrano, we are right on the cusp, right on the verge," Hearn revealed. "I think you could even get an announcement as early as this week. It has been a long time coming.
"The fight is twice as big it ever has been. April 30 is a target date. Madison Square Garden, the big room.
"The people in charge at MSG have said this a big room fight. This is a historic fight. It's never going to get any bigger than this."