Amir Khan has aimed a lengthy Twitter rant at Kell Brook, claiming the IBF welterweight champion is putting off a fight between the pair.
Brook will defend his title against Kevin Bizier on March 26 - the third defence of a belt he won by beating Shawn Porter in August 2014.
A bout with former IBF and WBA light welterweight champion Khan had been mooted, and the Olympic silver medallist has not taken kindly to the announcement of Bizier as Brook's next opponent.
Khan began a series of Twitter posts with a picture of a boxing ring with the words "Anytime any place #ready", which brought a response of "OK. June 4. Wembley Stadium" from Brook.
That was not the end of Khan's outburst, as he posted a series of scathing messages.
"[Promoter] Eddie Hearn is cool, I had a good chat with him at the [Calum] Smith fight in Liverpool and negotiations started before Christmas. I want it, Eddie wants it, Sky want it, all the fans want it, but then Kell decides to fight Kevin Bizier who's lost to Jo Jo Dan twice!," he tweeted.
"Never known of a world champion to have 3 bum defences back to back, make that 4 if you include Diego Chaves, at least fight someone in top 10. Mandatories can step aside, happens all the time, I was mandatory to Floyd [Mayweather] for 2 years with WBC.
"We could have fought in April, May or first week of June before Ramadan. I've got a potential fight with [Danny] Garcia if he wins 2moro for the WBC.
"I've been WBC number 1 for 2 years it's about time I got my opportunity to avenge that loss. Brook fight could still happen this year but Brook wants 50/50 split with me. Wake up son and smell the coffee! Be realistic and make it happen, even Eddie told you you're not worth that!
"Fact is they are fooling the fans fighting all these bums on the back of my name to hype his fights and profile saying I'm running scared. Brook v [Devon] Alexander called off 3 times, he turned down [Timothy] Bradley, [Brandon] Rios fight didn't happen, he retired poor [Juan Manuel] Marquez by mentioning his name 2 much.
"Seriously guys Imagine if I fought Jo Jo, Gallagher, [Frankie] Gavin and Bizier? I'd rather retire, I want the big fights and will continue to do so. Got let down by Floyd 3 times then [Manny] Pacquiao but plenty big fights out there including Brook, Garcia and some other huge fights too."
Khan's rant brought a response from Hearn, hitting back at the fighter's comments and setting out the details of a potential future bout.
He posted: "OK...I was asked not to say anything in media re our negotiations but guess that's been breached. On Monday I met with @AmirKingKhan lawyer, he asked for a £10m guarantee with upside to fight Brook with Kell getting approx £2 to £2.5m.
"After I spat my coffee out we said no thanks.
"Since then I have been in discussions with Al Haymon's team to try and get this made. We are willing to take the smaller split to get this made but enough of the insults. @AmirKingKhan we will make this easy for you 60-40 in your favour (Kell is World Champ) and you have it."
Hearn's tweets saw Brook goad Khan again, saying: "There you have it @AmirKingKhan - put up or shut up. No more talk, June 4 Wembley Stadium for the World title. I will destroy you."