Matchroom Boxing director Eddie Hearn has revealed exactly why Anthony Joshua's world heavyweight title bout against Wladimir Klitschko is yet to be confirmed. The high-profile clash has been in the offing ever since the former reigning champion's scheduled rematch against Tyson Fury was postponed for the second time last month when the "Gypsy King" was declared "medically unfit to fight".

Joshua was initially due to announce the next challenger for his IBF belt a fortnight ago after previous confirmation that a second defence would take place at the Manchester Arena on 26 November, although the situation changed markedly after it became clear that a fight with Klitschko was a real possibility.

With talks between the two camps seemingly progressing well, an official announcement over a 10 December meeting had been expected to arrive very soon.

David Haye, who compared the proposed contest to Muhammad Ali's last fight against Trevor Berbick in 1981, appeared to jump the gun by publicly suggesting that the deal had been completed. It now transpires that a decision over whether or not the WBA title recently vacated by Fury will be up for grabs is causing the delay.

"The deal is there but we are awaiting sanctioning from the WBA," Hearn, Joshua's promoter, told Sky Sports. "Both teams have written to the WBA to request sanctioning of our fight, but Wladimir wants the WBA belt to be on the line – so until that is approved we cannot move forward."

Klitschko held a version of the WBA strap for more than four years before his shock points defeat to Fury in Dusseldorf last November, while Joshua picked up the vacant IBF belt with a second-round knockout of Charles Martin in April after Fury had been stripped due to his refusal to defend against mandatory challenger Vyacheslav Glazkov. While Hearn is optimistic that a decision will come soon, he admits that other possibilities are currently being explored as a contingency plan.

"We expect news in the next few days, but in the mean time I believe both sides will look at alternative options for 10 December while we hope to get the news we need to make the fight happen," he added.