Wladimir Klitschko says proposed talks with David Haye over a heavyweight world title fight came to nothing.
IBF and WBO belt-holder Klitschko said Londoner Haye, 27, the undisputed cruiserweight world champion, had to learn to "behave himself".
"Our meeting didn't even start, you can't talk to him, it's impossible, he's nuts," Klitschko told BBC Sport.
"He has great potential, but he has to put some weight on and get some fights as a heavyweight. Then we'll see."
Klitschko, 32, added that any match with Haye could not take place this year because he has mandatory defences to honour.
"This year is impossible because I have two (mandatories) in a row," said the Ukrainian, who is in London to promote the launch of the boxing charity, Fight for Peace.
"The WBO is going to be the next fight on 12 July (against America's Tony Thompson) and the IBF will be at the end of the year."
Haye has had one fight in boxing's blue riband division, a first-round stoppage of Poland's Tomasz Bonin last April, but plans to relinquish his cruiserweight belts soon and become a heavyweight full-time.
Klitschko has won 50 of his 53 professional encounters at heavyweight and is generally considered to be the most credible operator in a weak division.
"David Haye is a very loud guy," he said. "I was in New York and I heard him screaming from over here. But I can't have a conversation with this guy.
"His manager (and trainer) Adam Booth is a really nice guy and tried to calm him down, but we couldn't have a conversation, unfortunately it didn't work.
"He has to establish himself and let his fists talk, not just talk. None of the heavyweights made so much noise as him, but talk is cheap, he has to show what he can do.
"Will I see him in the ring or not? If he wants to accomplish his goal he has to go through me."
Haye called Klitschko's recent victory over Russia's Sultan Ibragimov "pitiful" and is convinced he can become Britain's first heavyweight champion since Lennox Lewis retired in 2004.
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"I'd fight Wladimir Klitschko in my next fight if I could after his fight against Ibragimov," said Haye.
"That was embarrassing and he wouldn't look forward to fighting someone with my kind of style - powerful, explosive and able to take him out with any shot.
"I'm 100% certain that I'll achieve more things at heavyweight than I have done at cruiserweight.
"I'm not looking at boxing into my 31st year, so I've got two-and-a-half years to get the job done. If the titles get unified, hopefully I'll just have to fight one guy."
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