WBC world heavyweight champion Deontay Wilder and Tyson Fury's promoter Frank Warren have assured fans an announcement on their bout is imminent.
American Wilder and Briton Fury agreed a fight in October and Warren said official confirmation would follow.
But no further details have been made public, prompting doubts over a deal.
On Friday, Wilder posted on social media: "Announcement any day now. Thank you for being patient. This is going to be an amazing fight."
He added: "5:17am I'm up shadow boxing thinking about Tyson Fury. Oh boy, when I'm done with you, the only thing you'll be able to eat is New England clam chowder soup."
Eddie Hearn, promoter of British WBA, WBO and IBF world heavyweight champion Anthony Joshua, has stated publicly he has "doubts" over whether 30-year-old Fury and Wilder, 32, will meet in the ring.
Organisers are now working towards a date in December, with Warren insisting finding a venue date that suits broadcasters has delayed official confirmation and telling fans they "don't need to lose sleep" over the viability of the bout.
"The biggest fight in heavyweight boxing is on," he told IFL TV. "They are fighting. It's going to be on before the end of the year and we will announce it when it suits us.
"The venue we are negotiating, with we're waiting to confirm it can be there. It has to go to the best place as it's a mega fight."
Former world heavyweight champion Fury has fought just twice since returning to the sport after over two and a half years out, while Wilder has held the WBC title since January 2015.
Neither man has been beaten, with Fury boasting a 27-fight winning streak and Wilder producing 39 knockouts from 40 professional wins.