Manchester United is concerned David de Gea's delay in signing an extension with the club means he could ultimately reject it.

De Gea's current deal expires in 2016 and risk losing him on a free transfer in that summer.

De Gea came to United from Atletico Madrid, but he's been linked to a move to Real Madrid to replace Iker Casillas.

"It takes a long time now," Louis van Gaal said in a news conference. "So ... it can always happen. I am not the boss. I want him to stay. The player is the boss he can say yes or no. You will have to ask David de Gea not me. He has to sign. We have offered him a lot of money."