Neymar is demanding €30m from Barca he believes he is owed after leaving the club in August. The Brazil international has launched legal action to recover the money.
However, Sport says Barca are fighting back through the courts.
Barca spokesman Josep Vives has stated in the past: "The player did not meet the agreed conditions.
One was that "the player did not negotiate with another club in the last month before July 31" and the other was that he "publicly expressed his willingness to fulfill the contract".