Manchester United boss Louis van Gaal says it will be "a miracle" if his side win the league this season.

United face Sunderland on Sunday having lost their opening Premier League match of the season against Swansea.

Van Gaal, 63, is trying to rectify an "unbalanced" squad, though the club have refused to comment on a possible move for Real Madrid's Angel Di Maria.

"To win the title this season would be a miracle. But that isn't to say that it isn't possible," he said.

Winger Di Maria, 26, has told Real he wants to leave and Paris St-Germain are said to be unwilling to meet an asking price thought to be more than £50m.

That sum exceeds the British record fee Chelsea paid Liverpool for Fernando Torres in 2011.

Dutchman Van Gaal said United's owners are aware it would be "very difficult" to win the title this season.

  "I think the Glazer family understand this or I would not have accepted this job," he said.

Van Gaal signed a three-year contract to become United boss following his departure as Netherlands coach after the World Cup.

He won the title in his first season at both Barcelona and Bayern Munich, but believes a manager should be judged in his second year.

"What I did at Bayern Munich was a miracle because the team was not stable when I got there," he said.

"When I took over from Bobby Robson at Barcelona, he had won three titles, so there was stability.

"The problem I have at United is that the selection is not balanced. There are five number nines and six number 10s - and we don't have enough defenders."

United finished seventh in the Premier League last season, but former Real Madrid president Ramon Calderon believes Van Gaal will turn their fortunes around.

"They have a difficult situation," he told BBC Radio 5 live. "It is not usual to see Manchester United out of the Champions League.

"But I am sure Louis van Gaal can be a very good coach and take Manchester United to first position in any competition they play."