Wilfried Zaha  has completed his move from Crystal Palace  to Manchester United .The Premier League giants have announced that the 20-year-old will undertake a medical in Manchester on Friday after the two clubs reached an agreement for him to join United in July.The 20-year-old has agreed a five-and-a-half year contract and his registration will be transferred to United, even though he will be loaned back to Palace for the rest of the season.Goal.com understands that the deal is worth up to £17 million, with United paying £15m plus a further £2m in performance-related add-ons. Speaking on Friday, Sir Alex Ferguson said: “We like to sign young players with potential. We always feel we can develop players well here."That's been proved to be the case many times. We hope the boy will enjoy it here when he eventually comes."Zaha released a statement to say he is thrilled to be joining United but insisted his immediate sights will be fixed on winning promotion with Palace.“I am delighted to be joining Manchester United. However, my focus for the next five months will be solely at Crystal Palace."Palace chairman Steve Parish, who has been in Australia this week, had hoped to hang on to Zaha’s registration until the summer, with the two clubs agreeing a ‘guaranteed date of purchase’.However, Football League rules forbid such an agreement and United indicated their desire to wrap up the deal this week.As revealed by Goal.com on Monday, United blew Arsenal out of the water after the two Premier League big hitters became involved in a two-horse race to sign the coveted forward.United made the first formal move for Zaha last week and, due to interest from the Gunners, made multiple bids for the player after opening the bidding with a £6m offer.Parish had overseen the negotiations with the two clubs and was aware that Zaha met United manager Sir Alex Ferguson for talks in London on Sunday. The Championship club used Arsenal’s interest to drive the price way beyond the £10m mark and the final fee is far beyond what the Gunners paid to beat United to the signings of Alex Oxlade-Chamberlain in 2011 and Theo Walcott in 2006.The title challengers had initially been undecided about the framework of the deal amid concerns that the 20-year-old would be a ‘marked man’ if he remained in the Championship until the end of the season.The attacker, who can play anywhere across the front three, has been a driving force in Palace’s surge to fourth in the Championship, scoring five goals in 27 league appearances this season. He made his England debut as a substitute in the 4-2 November friendly defeat to Sweden.