The Ukrainian became the first unified champion in the division for 25 years when he defeated Tyson Fury last month but his undisputed reign has been short-lived with the IBF belt now up for grabs for the winner of Anthony Joshua's fight with Daniel Dubois that is scheduled for September.
In a video message posted on X, Usyk said: "Anthony and Daniel, I know the IBF title is important to you. It is my present to you on 21 September."
Usyk has asked for his belt not to be stripped so the undisputed title would be on the line again when he takes on Fury in a December rematch but IBF rules meant that Usyk had to be stripped of the title because he wasn't fighting mandatory challenger Dubois next.
The world champion previously described how he sacrificed nine months of his life to beat Fury.
He said after the fight: "I don’t think about boxing now. My start [of preparing for Fury] was September 2023.
"Nine months I worked; I missed happy new year; I missed my son’s birthday; I missed my other son’s birthday; I missed my daughter’s birthday; I missed my daughter’s birth. I missed my family’s holidays. All the time, training; training; training. My focus was only this fight.
"Now I’m happy. I want to go back home, go to my church, pray, say, ‘Jesus, thank you’. Because for me, and my country, it’s a big opportunity. I’m grateful for whoever prayed for me, because it’s many people. Thank you."
