Injury forces Klitschko out of Joshua title fight
Both fighters had been waiting for confirmation to announce the fight, which would have been for Joshua's IBF title and the vacant WBA belt, with a decision over the latter initially expected in the next few days.
However, Joshua's promoter Eddie Hearn will now seek an alternative opponent for the unbeaten British star to face at the Manchester Arena on December 10.
Klitschko lost his WBA 'super' title – along with the WBO, IBF and IBO belts – when he was defeated by Tyson Fury last November.
Fury gave up the IBF belt soon afterward that victory because of a rematch clause with Klitschko, and he also relinquished his remaining titles earlier this month ahead of a British Boxing Board of Control investigation into drug and medical issues.
"We've been in deep negotiations for a few weeks now waiting on the decision from the WBA,” Hearn said, according to Sky Sports.
"I was made aware that Wladimir picked up a minor injury late last week but regardless of that, with just over six weeks to go till December 10, it's unrealistic to put together a fight of this magnitude and give it the full build up it deserves,” Hearn added.
"There will be an official announcement on Joshua v Klitschko coming very soon, but for now we are seeking a new foe for December 10 and building a huge card for Manchester."