Tyson Fury has told Dillian Whyte to "step up and take your beating" after an extension was granted for the two fighters' camps to agree on the terms of a bout.
Fury and Whyte were permitted an additional 48 hours by the World Boxing Council (WBC) to negotiate their fight before purse bids are made.
The deadline had been 6pm on Wednesday but has now been pushed back two days, though the WBC confirmed that it would be the final extension.
A statement posted on the WBC's website said: "The World Boxing Council has received once again requests from the teams of Tyson Fury and Dillian Whyte, to extend the period of free negotiations.
"The WBC has granted this final extension and If there is no agreement, a purse bid will be held this coming Friday, January 28."
Whyte is the mandatory challenger for Fury's WBC heavyweight title but is currently in arbitration with the governing body.
After the announcement of the extension, Fury took to Twitter to say: "Time to step up and take your beating."
Fury's camp had previously made it known they wanted Anthony Joshua to step aside from his planned rematch with Oleksandr Usyk after the latter's triumph in September, which would allow the WBC champion to go up against the Ukrainian in a unification bout.
The Telegraph reported that Joshua had agreed to forego the rematch for a fee of £15million, though the former world champion denied claims a deal had been struck.
In a video posted to his official social media channels on Tuesday, Fury made it clear that he had had enough of waiting, saying: "Tick tick tock. The time has run out of the bottle. You're all getting a good hiding – cowards."