Jose Mourinho sees the Croatian as a key part of his recruitment push, though a fee has yet to be agreed.
The clubs are in contact, and Sportsmail understands the United manager wants the 28-year-old in his squad for next month’s
An insider said: “There’s a keenness to get it done. We’re looking at it going through within weeks.”
After signing £30.7m Benfica defender Victor Lindelof this week, Mourinho also wants Real Madrid striker Alvaro Morata.
Lindelof told the United website about his move: “Of course it feels great to know the coach wants you to finally be here. It makes me very happy. I’ve spoken to him. It was a good chat. It’s very important for me to hear what he has to say.”