Cristiano Ronaldo wants to sign a new deal at United, according to the player's agent, but only if the club can come up with a vastly improved contract. Ronaldo, who joined United two years ago from Sporting Lisbon for £12.5million as an 18-year-old, has already been tipped by Sir Alex Ferguson to become, alongside Wayne Rooney, one of the best players in world football.The Spanish press have tipped the Portuguese winger as a transfer target for Real Madrid. But, Ronaldo's agent, Jorge Mendes, expects his client to remain in Manchester."In three years he will be the best player in the world. I've got no doubts about that," Mendes told the Manchester Evening News."I think he will stay at United," he added, "but I also have to do the best for my client. He signed the existing contract at the age of 18, after only a handful of games for Sporting. Now he's developed into a star."Mendes is clearly pre-empting a pay-hike for his client, but Ronaldo's rise and rise since moving to United shows no signs of slowing down and will have to recognised by the club.His value to United is amplified at national level; he has scored seven goals for Portugal in their World Cup qualifying matches. He is second in Europe's goalscoring ranks, ahead of Andriy Shevchenko and Ruud van Nistelrooy."He has huge ambition. At Sporting there were lots of clubs after him - all the big names from Italy and Spain - but when I sat down with Alex Ferguson I knew it was the right choice."Sir Alex told me that Cristiano would play one week and then have a rest, then play, then rest and that he wouldn't be burned out."Report by Ben Hibbs.

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