Speaking to Sky Sports at the Luke Watkins v Lawrence Okolie final press conference on Monday, Hearn stated it remained touch and go as to whether Wilder would agree to fight in the UK.
Wilder offered Joshua $50m to travel to the USA for an undisputed clash, although was turned down by the unified champion who wants home advantage.
As negotiations hit a snail’s pace, Hearn backed up his fighter’s options by setting up a mandatory clash with Povetkin for September, whilst keeping his fingers crossed Wilder will get in touch to accept their UK deal.
“We’ve got to do everything we can to get this fight in the UK. If we can’t get Wilder to come, we have to look at taking the fight in the US,” Hearn told Sky Sports.
“Right now, we owe it to the UK fans to try and do this on home soil.
“We are one phone call away from a disaster and one phone call away from a party but that’s what we love about the game.
“We could have a conversation this afternoon and the Joshua v Wilder fight gets done. We could also have a conversation that Wilder is fighting (Dominic) Breazeale (his mandatory with the WBC) in September.
“Right now, what I can tell you is it’s going to be Povetkin or Wilder next. And it’s going to be that order either way – Wilder then Povetkin or Povetkin then Wilder,” he added.
Povetkin in September seems the most likely route before Wilder in the spring, provided the American can be persuaded to accept the terms on offer.
A rematch clause guaranteeing a second fight in the United States should be enough to seal the deal as both men compete to become the first undisputed heavyweight champion since Lennox Lewis two decades ago.