The Serbian midfielder has just one year left on his deal in Florence and Milan have submitted an offer of around €7million.
Fiorentina president Andrea Della Valle says Milan's offer is not enough and he hopes Ljajic will agree to a new deal.
"This morning I spoke with Adem, he is calm and told me he wants to stay at Fiorentina," Della Valle told a press conference.
"A €7million offer from AC Milan? I don't know the details, but if it is their bid, we are far from his value. I hope that the signature on the contract may come soon, but it depends on the demands of the players and his agent, who will meet our leaders the next week.
"Ljajic is a future champion, we hope he understands that our offer is interesting and that he may extend his deal with his in a few days."