Manchester United manager Louis van Gaal says Luke Shaw will train alone on the club's pre-season tour of the United States in order to improve his fitness.

The England international made 35 Premier League starts for Southampton last season and was selected in Roy Hodgson's England squad for the World Cup finals in Brazil but arrived on United's pre-season tour in inadequate shape according to Van Gaal.

Shaw became the most expensive teenager in world football after joining United for a reported £30m but despite possessing a reputation as one of the most exciting emerging players in the Premier League, the 19 year old must work to impress.

"He is OK, but I am always a trainer-coach who sees individuals and what they need," he said. "He needs to be fit and is not very fit and fit enough to do what I want. He needs to train individually until he is fit."

"I cannot judge that, but I see what I see. I have spoken with him and we have made a programme for him. He agreed with me," said the Dutchman.

"How long? That we have to see, but that I don't know," said Van Gaal. "I have heard good messages from Strud [Tony Strudwick, fitness coach] but we have to see."

Though Van Gaal's squad has been improved by the signing of Shaw and Spaniard Ander Herrera, the 62 year old is forced to work with the majority of the squad which achieved a worst-ever Premier League finish under David Moyes.

And Van Gaal has taken aim at the squad which he inherited from Moyes, claiming he has work to do to turn United around.

"No. I don't agree [it will be easy]," he said. "I had to follow Bobby Robson at Barcelona the year after he won three titles and there wasn't a problem.'

"When there is success you have a very good squad, and now I have to follow and the squad was broken I think.

"It is not in balance. It's more difficult to succeed in a difficult situation than in a fantastic situation."