The Real Madrid attacking midfielder is keen to return to the San Siro but the Rossoneri are not in a position to match the wages he can pick up in the Spanish capital.
Galliani admits the Italian fiscal system is threatening to scupper a deal for the 30-year-old Brazil international.
"It's hard, really hard," said Galliani. "The fiscal system kills us.
"Everyone must make an effort - Milan, Real Madrid and Kaka. A lot depends on his economical sacrifice."
He added: "The love between us and Kaka has never died. We were forced to sell him and now let's see what we can do."
Kaka scored 95 goals for Milan in a six-year stay with the club from 2003 to 2009 during which time he won the UEFA Champions League.