Manchester United manager Louis van Gaal has admitted goalkeeper David De Gea will sign a new contract at Old Trafford.

The Spain international's current deal runs down in the summer of 2016 and after a disappointing start to his United career, the 24-year-old has emerged as one of the best keepers in the world.

De Gea has been constantly linked with a move to Real Madrid, while their star player Gareth Bale is on the radar of the 20-times English champions. United secured the services of Victor Valdes earlier this week and his addition has raised further concerns over De Gea's future at Old Trafford.

However, the former Barcelona and Bayern Munich manager remains relaxed over the United star's contract situation, despite reports linking De Gea to Real.

"I think so, yes. I think there is no problem for him to sign. It's the same as other players. You can ask other players and I can answer the same," Van Gaal explained.

"It's always like that; when you are a fixed line-up player, then probably you are the best and then the manager is very happy that a player that is fixed in the line-up will stay. It's always like that."

United have further received encouragement in retaining De Gea after Real skipper Iker Casillas has warned the Spanish capital club against signing the Premier League star keeper. The Red Devils star is tipped to be the long-term successor for Casillas for both club and the national team.

Casillas still has two-and-a-half years left on his contract at Real and has warned Carlo Ancelotti's side that he has to play regularly in order to continue with his current employers.

"I told them that I must play or go," Casillas told Cadena Cope.

"The only thing is that if you start the season and you're not playing, you must understand and respect the coach's decision to choose someone else. I want to play, but I've never demanded to play."

"The club have behaved in a very loving way. They have always tried to motivate me during difficult times. I'm not thinking about June, only the next morning."

"At the end of the day, I've received so much [from Madrid]. I'm back focused on enjoying my time here, I feel important again and hope to exploit the opportunities I get," he added.