Anthony Joshua has been granted an exception by the IBF to fight Wladimir Klitschko for their heavyweight title, but the bout must take place before December 2.
Joshua’s promoters Matchroom Boxing requested the special extension and it was approved by the IBF at their convention.
The governing body has ruled that the winner of any potential rematch between Joshua and Klitschko must then face No 1 contender Kubrat Pulev in a title defence.
The IBF have also stipulated there will be no further exceptions or unification fights beyond December 2.
Pulev had objected to the exception being made but has accepted the condition that he will receive his shot at the IBF world champion after the rematch.
A number of venues are being considered to stage the second meeting of Joshua and Klitschko, who contested an excellent fight at a sold-out Wembley Stadium in April.
“We’ve had so many offers – Nigeria, Dubai, America, and also we have the opportunity of Cardiff here in the UK,” promoter Eddie Hearn said after the IBF decision.