MADRID (AFP) -- Manchester United coach Sir Alex Ferguson insists he is going nowhere but former United star Ruud van Nistelrooy says Portuguese winger and former clubmate Cristiano Ronaldo would be more than welcome were he to opt for a new challenge in Madrid.

According to Spanish media reports the Spanish giants would be willing to pay United 50 million euros (65 million dollars) for the popular 21-year-old Portugal international, who has been in brilliant form this season.

That would make him the club's third most expensive signing ever, after Zinedine Zidane (94 million dollars) and Luis Figo (72 million dollars).

Ronaldo's contract at Old Trafford runs out in 2010, and United's assistant boss Carlos Queiroz said recently the club are already planning to start negotiations on extending that deal.

AS sports daily Friday quoted Van Nistelrooy as saying he would be happy to welcome another Ronaldo to the Bernabeu with the "other" Ronaldo having just been shipped out to AC Milan.

"He is a fantastic player. This year he's been playing better than at any time since he joined Manchester, scoring lots of goals and playing well.

"He is very young and has the experience of a World Cup behind him," during which the starlet managed to help knockout the England of strike partner Wayne Rooney. But van Nistelrooy added that any deal would be "between Madrid and United."

"If players like him come then they will always be welcome," said the Dutchman, adding that reports of his fractured relationship with Ferguson, which the media claimed promoted his ousting from Old Trafford, were "nothing serious." The striker explained: "It was nothing serious. The press talk a lot, but lies."

On the situation of David Beckham, who is Los Angeles-bound and has been frozen out of the first team picture, Van Nistelrooy said: "It's a difficult situation for David. It's difficult for us too as we want the best for him. He's a great professional and has shown that all through his career."