Manuel Charr has claimed he has been aproached to fight Anthony Joshua on June 1.
Joshua looks certain to need a new opponent for the next defence of his heavyweight world titles after Jarrell Miller failed a drugs test.
The American faces a hearing with the New York Athletic Commission – and a possible ban.
Joshua is still expected to fight at Madison Square Garden with Charr and Adam Kownacki among the frontunners to challenge the Brit.
The former has won 31 of his 35 fights and holds the WBA 'regular' world title.
But he is unlikely to prove a test for Joshua having gallen short against Mairis Breidis, Johan Duhaupas and Alexander Povetkin over the last five years.
Charr posted on Instagram : "Now, internal negotiations are taking place regarding the fight in June; Mahmoud Charr against Anthony Joshua.
"I am very happy about this task and the challenge. I'm ready to go to fight against Joshua and bring home the victory.
"As the # 1 WBA and reigning world champion, I'm the most worthy opponent for Anthony Joshua. I am the suitable and official challenger. For Joshua's honor, it's important to fight against the # 1 WBA rankings in the world."
Charr was also due to face David Haye in 2013 but the Brit was forced to pull out with a hand injury.
Joshua's old rival Dillian Whyte has thrown his hat into the ring but is highly unlikely to be considered.
Whyte told talkSPORT : "I would jump in and have some. I would take the fight with Joshua at the drop of the hat. I would fight him seven days a week.
"If they want it, they can have it. Simple as that.
"I can whip myself into shape for the right opportunity. I can just push for a few weeks and get sparring.
"When opportunities like these present themselves you’ve got to take them.
"I don’t know all the ins and outs [of Miller’s doping results] so until the full report is produced, we don’t know if it’s something simple or it’s something major.
"We’ll wait and see."