The Milan CEO has conceded that signing the attacking midfielder will be difficult, as the Spanish champions have stressed he will only leave for the right price
The Rossoneri are desperate to re-sign the Brazil international, but they have so far been unable to reach an agreement with both club and player, as the club's poor financial position continues to hamper their off-season transfer dealings.
"Operation Kaka is a very complicated matter. I would say that it is nearly impossible. The costs are enormous, we are talking about very high wages," Galliani told Sky Sport Italia.
Meanwhile, Real Madrid coach Jose Mourinho vowed that the Liga champions will only let go of Kaka for the right price.
"The most important thing is that he is happy. He is a great player at a high level. If he stays, it would be perfect for me and if not we will notice the difference," he told reporters.
"We will not let go of him on a free. If a team wants him, they will have to pay up."
Kaka is under contract at the Santiago Bernabeu until June 2015, and assisted three goals in the Blancos' 5-1 friendly demolition of Milan in the United States on Wednesday.