“Fury and Usyk are close to signing a contract to fight for the title of undisputed world champion.
It will take place at Wembley Stadium in London on 29 April.
Both parties have notified the WBA that they have agreed on the terms, ”ESPN quotes Mendoza as saying.
Fury, 34, is undefeated in the professional ring.
He has 33 wins and one draw.
Usyk on August 21 in Jeddah defended his belts in a duel with Anthony Joshua.
The Ukrainian also knows no defeats in the professional ring - he has 20 victories.
Fury has previously said that he is ready to fight anyone.