Louis van Gaal has expressed his dissatisfaction at the tenure of the summer transfer window and insists that the window needs to be closed before the season begins in August.

The manager insists that they cannot repeat their mistakes from the transfer market this season and complete their deals sooner to help foster some familiarity in the squad.

Manchester United waited late in the market to complete the signing of Angel di Maria and allowed Danny Welbeck to leave on deadline day to Arsenal, where he scored the winning goal for the Gunners at Old Trafford which helped them progress into the finals of the FA Cup at Wembley.

Van Gaal has his work cut out this season, with the Dutchman likely to make a plethora of changes to the squad to hoist a title challenge next season. It was a successful debut season for the former Bayern Munich manager, leading his side to a top four finish after a seventh place slump under David Moyes last season.

However, the fans will now be looking at him to take the team even forward and come closer to match the likes of Chelsea, who deservedly claimed the title this season.

The Dutchman believes that the task has been that much more harder because with the transfer window running late, they have to start the season without completely bedding the players in, which creates major problems midway through the campaign.

When asked if the upcoming transfer window is the most challenging in his career, he said, "You can never say that in advance, because what I have said is it's a process. It's not so easy, because when you sell a player there are also three parties.

"The same when you buy a player and you never know which party is struggling or not struggling. It's also ending on 31 August or 1 September and that's ridiculous in my opinion.

"I have strived many times to change the transfer period. It has to be finished before you prepare your team for the season. Last summer we had the World Cup and then a lot of players came late in.

"We had a lot of purchase at the last month so we have to prepare our team in the Premier League and that costs us a lot of points. Now I hope we shall finish our business much earlier."