Anthony Joshua has been ordered to defend his WBO heavyweight title against mandatory challenger Oleksandr Usyk following the apparent collapse of his fight against Tyson Fury.

Fury announced earlier this week he would take on Joshua in Saudi Arabia on 14 August, only to be informed hours later by a United States arbitrator that he was contractually obliged to fight Deontay Wilder for a third time.

In the wake of that ruling, the WBO contacted Eddie Hearn on Wednesday, giving Joshua's promoter 48 hours to show a reason why a fight with Usyk should not be mandated.

Hearn requested an extension until Monday morning to the "show cause" notice in order to "discuss the subject matter and other related affairs" with Joshua, but that provoked an objection from Usyk's team.

The WBO sided with the Ukrainian, who had previously agreed to step aside to allow Joshua-Fury to go ahead, and said in a statement on its website: "The extension request is hereby denied."

As a result, the two fighters and their teams have until 31 May to reach an agreement for a fight or purse bids will be called.