Eddie Hearn is trying to determine whether Deontay Wilder is serious when he claims he wants to fight Anthony Joshua in the UK.
The American tweeted that he was happy to accept an offer from the Joshua camp to come over for a unification bout later this year.
Joshua is already pencilled in to take on WBA mandatory challenger Alexander Povetkin, but a fight against Wilder could yet take place before that.
Hearn told Sky Sports News: “Our original plan and hope was to do it in September but with (Mexican) Canelo (Alvarez) fighting on September 15 it makes it a little bit more difficult with US TV.
“The fact that we’ve lost four weeks waiting for an answer from Deontay Wilder makes a fight happening in 11 or 12 weeks of this magnitude unlikely.
“I think if it is before Povetkin then it runs on October/November. It’s all come as a bit of a shock that Deontay’s finally come back to us on the offer and seems to accept the terms. Now we have to find out if it’s bluster or if it’s real.”
Hearn added: “We’ve got to get to the bottom of it today, but one thing I can tell you is that by the end of this week Deontay Wilder will have a contract in front of him and we’ll see if he’s real.”
On a potential venue, Hearn said: “I think Wembley is where Anthony Joshua wants it to take place. He had a brilliant night there against Wladimir Klitschko and it seems a natural home.”