Nathan Cleverly will make his sixth world title defence at Cardiff's Motorpoint Arena on August 17, but the identity of his opponent remains up in the air.
Cleverly, the WBO light-heavyweight champion, had agreed in principle to fight Sergey Kovalev, but the IBF have now ordered title holder Bernard Hopkins to fight the Russian after he became mandatory challenger following his knockout win over Cornelius White last Friday.
Kovalev must now decide whether he wants to take on Cleverly in Wales, or Hopkins in the United States next.
Cleverly's promoter Frank Warren says he has been in negotiations with HBO, who want to screen the fight, for over a month, but the Welsh fighter may now have to find another opponent to take on in what will be his second fight at the Cardiff venue.
"We were hoping today to announce Nathan's next opponent for a fight that is due to take place on August 17," Warren said at a press conference in central London.
"We were hoping it would be against Sergey Kovalev.
"We agreed terms with HBO, who approached us with this fight in May.
"Originally we intended to put the fight on in July. We were asked to put that back, which we did because Kovalev had to fight an eliminator last Friday and then moved the date to August 10. We booked the venue, then they asked us to push it back to August 17.
"Over the last few days we have had conversations about applying for visas for Kovalev. I was on the phone until 5:30am to HBO.
"They are calling in the Main Events people today to say you are fighting or not? So today we will know if Nathan will be fighting Kovalev.
"That's the fight we want but if he doesn't want it we will find someone else."
Kovalev, 30, is one of the hottest fighters in the 168lb division, knocking out his last five opponents.