Vitali Klitschko will defend his WBC heavyweight title against London-based Pole Albert Sosnowski on May 29 - and then flip a coin with brother Wladimir to decide who fights Britain's David Haye.
Haye won the WBA heavyweight title by defeating Russian giant Nikolay Valuev in November and faces the first defence of his title against American John Ruiz next month.
Assuming he wins that contest, Haye has his sights set on unifying the heavyweight division and that would mean defeating WBC champion Vitali and his brother Wladimir, the IBF and WBO champion.
Plans to fight both Ukrainian brothers have fallen through before, but Klitschko appears keen to make the fight happen later this year.
"I told my brother, 'I want to fight Haye', but he said no, he wants to fight him," Klitschko said ahead of the Laureus World Sports Awards in Abu Dhabi today.
"For him it is personal, but for me I want the title. My brother already has three but I have to clear it with him. I hope he listens to his older brother.
"Always you need motivation and the motivation is to have all the titles in the family.
"Everyone wants to see a unification. Champion against champion. Haye has the choice, one of the brothers Klitschko.
"I'll tell him it's easier to beat me, because I'm older and I don't have as much energy as my brother.
"I keep my fingers crossed that Haye beats Ruiz. Not because I like him, but I want his title and to shut his mouth. Maybe we decide by coins who fights him. Let's hope my brother listens to me. He must always respect old people.
"If someone had told me when I was 20 that I'd be boxing at 38, I wouldn't believe them. But now I am 38 but I think I'm 17, unless I see my grey hair in the mirror."
Klitschko had looked set to face Valuev but, when that fight broke down, European champion Sosnowski stepped in and will challenge for the title in Gelsenkirchen, Germany.
Klitschko branded Valuev a 'chicken' for turning down USD2.5 million for the fight and demanding USD4 million instead, but insisted he would not be taking Sosnowski lightly.
"Sosnowski is the European champion," he added. "He's pretty strong, he's not famous but he's only 31 and coming up. I don't want to underestimate him. I think my chances are 50-50.
"It's a big chance for him but I want to show my skills and show I'm the best in the world."
News of the fight is a blow to Britain's Audley Harrison, who had been due to challenge Sosnowski for the European belt in London next month.
Warsaw-born 31-year-old Sosnowski (45-2-1, with 27 knockout wins) won the European title by dethroning Italian Paolo Vidoz and had previously upset Briton Danny Williams.
He unsurprisingly pulled out of the Harrison fight and said: "It's a dream come true. Because of the Harrison fight I am already in training and suddenly here comes the once-in-a-lifetime chance to fight Klitschko. I want to thank him and his team for giving me that opportunity, which I will definitely take.
"For me, Klitschko is already over the hill. I know that I am the underdog for everybody, but I tell you, Klitschko will regret that he picked me."