Tony Bellew's mooted fight against Oleksandr Usyk is in the final stages of being agreed, according to both fighters' promoters.
Pound-for-pound supremo Usyk immediately called out Bellew after winning the World Boxing Super Series and becoming the undisputed cruiserweight champion in July.
A November 10 date in London or Manchester has been allocated and, according to Bellew's promoter Eddie Hearn, in the "next two weeks we'll know if it's happening - there is a good chance".
Hearn told Sky Sports: "Ever since Usyk called him out after the Series, Tony's had it in his head that he's fighting him.
"And it's the only fight that he will come back for. It's Usyk or retire. That's what it will be now. It's only really the Usyk fight that gives him the buzz."
Usyk's promoter Alexander Krassyuk told Sky Sports: "We are very close to finalising the deal and announcing the fight. Most likely it will take place on November 10 in the UK."
The Ukrainian southpaw has torn through the professional ranks, winning all 15 fights since claiming an Olympic gold medal at London 2012.
Usyk took the WBO and WBC belts into the World Boxing Super Series final against Murat Gassiev, where a 12-round masterclass earned him the IBF and WBA titles too.
Bellew is now on the verge of an opportunity to hold all four major belts at cruiserweight after back-to-back heavyweight wins over David Haye.
"When you get an opportunity like this to be undisputed champion, something that he's dreamed of since he laced up a pair of gloves, he can't let it go," Hearn said.
"But this will be his last fight, I will make sure of that, and he will give every ounce if it happens."
Bellew, aged 35, has not had to make the cruiserweight weight limit in two years since defending his world title against BJ Flores.
"He's started now in camp, because if it's November, it's 11 weeks and he's got to get his weight down," Hearn said. "He's on that already. He was out in Portugal last week training, and he's in a good place."
Returning to the scene of his Olympic gold medal victory would be welcomed by Usyk, whose promoter Krassyuk added: "Oh, England is the motherland for boxing. Every intelligent person is aware of that.
"Usyk has become the Olympic champion in England and he is looking forward to defending all of his four belts. That will be a great honour for him and his team!"
Usyk has previously made his intention clear to step up to heavyweight and challenge Anthony Joshua.
"The boxing world would desire the clash of two Olympic champs and two [future] undisputed professionals," Krassyuk told Sky Sports last month.
Watch Anthony Joshua defend his world heavyweight titles against Alexander Povetkin at Wembley Stadium, on September 22, live on Sky Sports Box Office.