Speculation over Ljajic's future has rumbled on for much of the summer as the 21-year-old entered the final year of his contract with La Viola.
Ljajic has refused to discuss signing a new contract in Florence, despite the club turning down a bid from AC Milan last month.
Della Valle has admitted that Fiorentina need to get the situation sorted as a matter of urgency, conceding that he expects the Serbian to find a new club in the next seven days.
He told reporters: "We will resolve the Ljajic situation, 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."