Barcelona, Chelsea, Real Madrid and Malaga are all reportedly in the race to acquire the Argentina international.
Palermo confirmed last month they had received a 50million euros bid from an unnamed club to acquire the 22-year-old's services.
"The only Palermo player that is in the market is Pastore," said Zamparini.
"The situation must be resolved in the next 15 days, otherwise, the player will remain with us.
"Before the Copa America ends, Pastore's future must be decided.
"There is a 90% chance that Pastore will leave because that is his desire and when you hear about the clubs that want him it's only normal.
"We would be sad to see him go, considering he is the only star that I've had as president."
The highly-rated playmaker, who is currently competing at the Copa America, joined Palermo in 2009 from Huracan for 19million euros and was the team's leading scorer in Serie A last season with 11 goals.
He is under contract with Palermo until June 2015.
Source: Team Talk
Source: Team Talk