A source close to negotiations admits negotiations between Palace, ASSE and Mateta's parent club Mainz are continuing.
Mateta is expected to start for Palace in their FA Cup clash with Millwall, but a move to ASSE remains the priority.
The source told L'Equipe: "ASSE wants him. The player agrees to come. Now it remains to find an agreement between the three clubs, Mainz, ASSE and Crystal Palace.
"It's a little complicated because there is a question of salary distribution, to know who takes what."
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