Boxing promoter Eddie Hearn has confirmed Anthony Joshua's new opponent for his next fight will be announced early next week.
Joshua was due to defend his WBA, IBF and WBO heavyweight belts against American Jarrell Miller in New York on June 2 (NZ time).
But the bout is in jeopardy, after Miller tested positive for banned substance GW1516, which boosts endurance and helps athletes burn fat.
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The positive test led to the New York State Athletic Commission denying his application for a boxing license in the state.
As the fight is six weeks away, Hearn needs to act swiftly to secure a new opponent and he already has a shortlist of potential candidates.
"Obviously, it's a fight in America, so from our point of view, we would like an American challenger really," Hearn told Sky Sports UK.
"You go through the list - Luis Ortiz, Adam Kownacki, Michael Hunter, Manuel Charr, Agit Kabayel, the European champion who beat Derek Chisora.
"There's probably 7-8 guys I think would fit the bill. Being an American debut, in an ideal world, we would like it to be an American or someone that fights in America.
"We're going through that, and we're going to be working hard in the next couple of days. There will be an announcement from us in the early part of next week, locking in Anthony Joshua's next opponent."
Miller returned the "adverse finding" on March 20 and his team have now requested his 'B' sample be tested.
"I am absolutely devastated upon hearing the news my boxing license has been revoked in NY State and I will be vigorously appealing this decision," he said in an Instagram post.
"I have never knowingly taken any banned substance and when I found out the news last night, I was totally shocked.
"This was a voluntarily test that I was very happy to do and these results came just one week after another voluntarily test that I had taken, which was completely clean.
"I refuse to just lie down and let my dream be taken away from me, when I know in my heart that I've done nothing wrong.
"I don't have anything to hide and the truth will make itself known."
When the news broke, Kiwi fighter Joseph Parker put his hand up, saying he was "very willing and ready" for a rematch with Joshua, who beat him on points to take his WBO belt in Cardiff last year.
But Hearn was quick to respond to Parker's comments, saying he wasn't an option.