WBC president stated that the Ukrainian boxer is fully obligated to step into the ring against the German challenger.
"The WBC's ruling was that one fight was voluntary, and then the winner had to face Kabayel," he said in an interview with Pro Box TV.
"This fight was sanctioned today, and it is a mandatory defense for Usyk. By the way, I am smiling. Everyone criticized the WBC for allowing and sanctioning the fight with Rico [Verhoeven] for the WBC title. Today I can proudly say that we did the right thing."
Usyk recently defeated Verhoeven via technical knockout just one second before the end of the 11th round to successfully defend his WBC world heavyweight title.
The 33-year-old Kabayel has won all 27 of his professional bouts, with 19 coming by way of knockout. The German heavyweight has secured stoppage victories in his last six consecutive fights.