The Brazil international has fallen down the pecking order and has lost his starting place in the team in the last year, and his situation is expected to worsen with the anticipated arrival of Gareth Bale from Tottenham Hotspur.
Kaka is quoted as saying by Sky Sports News: "I want to leave. I think now is the right moment for me and for the club for me to leave amicably.
"I have spoken to Ancelotti and with the club, they all know. Things are difficult for me now in the team, and the club knows what I want.
"It's my obligation to work and keep training, but my father is already working to see if something comes up. I think it's the best thing for me and the club."
Kaka scored twice in his side's friendly win over Deportivo La Coruna on Thursday.