Tyson Fury and Anthony Joshua's undisputed fight is now likely to take place in February.
The heavyweight rivals had been on a collision course for the end of this year before the coronavirus crisis struck.
Both men had been due to defend their respective world titles in June and July but both have been pushed back.
Fury is likely to take on Deontay Wilder for a third time on October 3 while Joshua has targeted a July return against Kubrat Pulev.
There had been a suggestion that Wilder and Pulev would accept a step-aside payment to allow the Brits to clash.
But Fury's promoter Bob Arum has ruled that out and told British fans they must wait until 2021.
"Wilder wants to fight Fury again," he told IFL TV. "He's not indicated to us or anybody else that he would be willing to step aside. A further question is who is going to pay him to step aside?
"And, anyone on our staff has not even raised the possibility with us. So as far as we’re concerned, we’re thinking ahead to a third Fury vs Wilder fight.
"We’re Pulev’s co-promoter and nobody has discussed with us a step-aside [payment]
"I speak with authority on this because of my relationship with Pulev and my role in Fury and Wilder, and there has been absolutely no discussions by anybody about either of those guys [Wilder or Pulev] stepping aside."
Arum also doubts Joshua will be able to face Pulev in July with the fight due to take place at the Tottenham Hotspur Stadium.
He added: "I think scheduling for July is a bit optimistic, I don’t think we’re going to be able to get clearance to have spectators at the event in July.
"I think that that fight would go over into the fall as well as the Fury – Wilder fight, which we’re now looking at October.
"I think that fights play out the way many people think and Joshua and Fury are the winners, they’ll fight some time next year.
"No great catastrophe if they don’t fight in December and fight in January or February 2021."
