The Spaniard joined United in January, but has only made one senior appearance for the Red Devils.
Manager Louis Van Gaal also accused Valdes of refusing to play for United's Under-21 side earlier this season and the former Barcelona keeper has been frozen out at Old Trafford.
Valdes' agent Gines Carvajal has confirmed that his client is likely to leave United in January though he is hoping to remain in English football.
Carvajal said: "We are relying on Manchester United letting Victor go. The Premier League is very attractive and Valdes wants to stay because he has adapted perfectly to England, but we are not closing the door to any options."
"There are still two months until the transfer window opens and there is nothing concrete, but the intention is to leave Manchester United."