Manchester United striker Wayne Rooney has admitted that it has been "difficult" watching the club's fierce rivals Liverpool go from strength to strength this season.

The Merseyside outfit are currently second in the Premier League table, seven points behind leaders Chelsea with a game in hand.

It's a different story for United though, as they look likely to miss out on a Champions League spot due to residing nine points adrift of fourth place.

"To see [Manchester] City doing well, and particularly Liverpool, is really difficult," Rooney told Inside United. "It's not nice when we know we are capable of being up there challenging and we haven't been doing that this season.

"However, it means we have to step up and get back up there because the feeling we've had this season is not a nice feeling at all to have. We have to keep working, keep progressing and finish the season stronger."

United will take on Liverpool at Old Trafford on Sunday.