VfB Stuttgart chief Alexander Wehrle retains hope of keeping hold of Deniz Undav.
The striker has been on-loan at VfB this season from Brighton.
VfB can sign Undav permanently for 20m, with the player seeking 5m-a-year.
"We are in very, very good talks with Deniz and his agent," said VfB managing director Wehrle.
"I am very confident that we will achieve a positive result together in the end - but we are not there yet."