Tyson Fury's heavyweight unification fight with Anthony Joshua could be put on hold after an independent arbitrator ruled that the WBC heavyweight champion must face former champion Deontay Wilder in a rematch.
Retired judge Daniel Weinstein upheld a claim lodged by Wilder that Fury must face him in a third fight by September 15 following their February 2020 title battle.
While the arbitrator's ruling is not a formal court order, it would be deemed enforceable by courts if Wilder and Fury are unable to reach agreement.
Fury's promoter Frank Warren told the BBC on Tuesday he hoped Wilder would, for a lucrative fee, agree to step aside and allow the bout to go ahead.
"Until we can reach an accommodation with Deontay Wilder's people, I can't say that (Fury's fight with Joshua) will definitely happen," said Warren.
"But we are working hard to get that over the line.
"We were talking last night and hopefully we can do that.
"If not then Tyson, if he wishes, will go to the fight with Wilder. They're the only two options."
Monday's ruling comes just a day after Fury announced he had agreed to fight Joshua in Saudi Arabia on August 14 where the WBC, WBA, IBF and WBO heavyweight belts will be up for grabs.
"Massive announcement FURY VS JOSHUA IS ON AUGUST 14 in The kingdom of Saudi Arabia. The worlds (sic) biggest sporting event all eyes on us," Fury wrote on Twitter, describing the bout as "100 percent on".
Weinstein's ruling on Monday did not grant Wilder any monetary damages and also said an extension to the September 15 deadline was permissible if both the Wilder and Fury camps could reach agreement.
Wilder's camp had argued their fighter had a contractual right to a third fight with Fury.
But after delays caused by the coronavirus pandemic led to last July's contest being postponed, Wilder's team sought to move the bout to 2021.
Fury refused the 2021 date and said he would move on which prompted the mediation.
Neither Fury nor Wilder have fought since clashing in Las Vegas in February last year, where Fury outclassed the previously unbeaten American to win via a seventh-round technical knockout.
The two fighters had previously clashed at the Staples Center in Los Angeles in 2018, battling to an epic draw after Fury survived a 12th round knockdown.