Mancini is hopeful he could tie up a deal for the Frenchman "before the end of the month".
Nasri has one year left on his contract with the Gunners and has been linked with a move away from the Emirates Stadium.
Mancini told Sky Sports News: "Samir is under contract with Arsenal. Also for Samir it depends on many things."
Asked if an offer has been made for Nasri, Mancini continued: "I don't know in this moment, I don't know the situation but for Nasri it is difficult.
"I hope that we can buy because we need other players, and I hope that this player can arrive before the end of the month."