Ramon Calderon, the Real Madrid president, says Manchester United should be “happy and proud” to allow Cristiano Ronaldo to join the Spanish champions.

Calderon, who was expected to meet David Gill, the Manchester United chief executive, at the inaugural meeting of the European Club Association (ECA) in Nyon, Switzerland today, has told Spanish newspaper AS, that the Premier League club should not be angry with them, but realise they have a chance to be part of the “transfer of the century”.

Only yesterday Calderon appeared to concede defeat in his attempts to convince United to sell the Portugal international. However, his latest outburst seems to show the fight may still have some way to go.

"I think that, first of all, it's the desire of the player (to join us),” he said. “But, of course, Manchester shouldn't be angry and they should open up their stance.

"We can't be blamed if nearly every player wants to come to Real Madrid. If I was Manchester United I'd be happy and proud to be able to negotiate such a transfer for one of my players.

"Everything would be a lot easier if United realised that they could pull off the transfer of the century."

Calderon, who was at Wimbledon to watch Rafael Nadal’s triumph yesterday, insists he has not given up hope of signing Ronaldo, insisting the decision rests with the player.

"It depends on the player, on Ronaldo,” he said. “Since I've known football it has been the case that the desires of the footballer are what decide matters.

"If Ronaldo wants to leave Manchester, he'll leave. If he wants to stay, he'll stay.

"I don't think you can keep anyone in a place where they don't want to be, not even in a family. But I insist that for a formal negotiation to start Manchester United will have to open their doors to us. Manchester have to want to talk."

Ronaldo today underwent surgery on his right ankle in Amsterdam after he revealed after Euro 2008 that he had been playing in pain for the last three months.

"Cristiano Ronaldo underwent surgery today to his right ankle," United said in a statement: "The operation was performed by Professor C. Niek van Dijk at The Academic Medical Centre in Amsterdam and the initial indications are that the procedure was successful.

"Cristiano will begin his convalescence under the direction of club medical staff and an estimation of his return to full fitness will be possible following review by the specialist in one month."

Ronaldo is expected to miss the start of the new season, a development that threatens to complicate his potential transfer from United to Real Madrid. However, Calderon insists Real are not concerned by the injury.

"At the moment that is something which should only concern the player and United,” Calderon said.

Sir Alex Ferguson, the manager, remains opposed to selling the 23-year-old, as do David Gill, the chief executive, and, contrary to reports in Spain yesterday, the Glazer family, who own the club.

Real are willing to pay a world-record fee in excess of £50 million to sign Ronaldo — and, according to sources in Spain, would be prepared to bid more than £80 million to get their man — but United maintain that he is not for sale. They have appeared to be in denial about Ronaldo’s intentions for much of the summer, but now that he has spoken of his “dream” of moving to Real, their stance has hardened.

There is a point of principle involved, with the club determined to hold the player to a £100,000-a-week, five-year contract that he signed only 15 months ago, but there is also a strong element of pragmatism, with Ferguson aware that selling Ronaldo would be a backward step for the team who won the Premier League and Champions League last season.

United are convinced that they will keep hold of Ronaldo, but much will hinge on how far the player is prepared to go in order to get the transfer he craves. He has told friends that he will do “whatever it takes” to engineer a switch to Spain, but Ferguson considers it significant that Ronaldo has not released the statement that he planned to make almost a fortnight ago in order to accelerate his move. The view within Old Trafford is that his transfer simply cannot and will not happen, whatever the money offered by Real.