Fassone said the Serie A club would do all they could to have the ban overturned, with their initial appeal heading to the Court of Arbitration for Sport (CAS).
"We consider the UEFA ruling unfair," he said on Monday.
"I hope the CAS will see things differently and we will fight until the very end to overturn the sentence."
Though Milan will not, as it stands, be permitted to compete in Europe's second-tier club competition, they would be free to play in the Champions League or Europa League in 2019-20 should they qualify for either tournament.
Milan were taken over by a consortium headed by Chinese businessman Li Yonghong, who then became the club's chairman, in April last year.
The club subsequently spent big before the 2017-18 campaign, signing the likes of Leonardo Bonucci, Andre Silva and Hakan Calhanoglu.