The Eastlands outfit are willing to pay £6m for the 20-year-old Montenegrin.
But Partizan - who face a Champions League qualifier next month - want more cash so they can replace the defender.
The Serbian club's director of football Mladen Krstajic said: "Savic is still here with us, so he has signed nothing yet.
"If we lose him we would be in a trouble defensively. He can leave only if we find adequate replacement at the back."