The club are looking to cash in on the Serbia international, who scored 11 goals in Serie A last term, after he turned down an offer to extend his contract which expires next year.
Milan have already seen an offer turned down for the 22-year-old, while Roma are also thought to be interested.
Della Valle is determined to sell and not let the player run down his contract as Riccardo Montolivo did when he joined Milan on a Bosman last summer.
"We will resolve the Ljajic situation," Della Valle told reporters on Monday. "Hopefully as soon as possible.
"The chances of a Milan move? I won't say no to anything. Ljajic will almost certainly leave Florence though, there will be no repeat of the Riccardo Montolivo situation."
Meanwhile, Fiorentina are keen to sign 20-year-old RNK Split striker Ante Rebic.
The club's sports director Daniele Prade told Sky Sport Italia: "Rebic? We really like him and we'll try to strike up a deal. He has great qualities, he has the features that we seek."