Ronaldo has been at Old Trafford since joining from Sporting Lisbon in 2003
Real Madrid president Ramon Calderon has dismissed rumours they have agreed a deal to sign Cristiano Ronaldo.
Earlier this week Real director Pedro Trapote was quoted as saying a deal for a summer transfer had been struck.
That was denied by Manchester United boss Sir Alex Ferguson, who said he "wouldn't sell a virus" to "that mob."
And Calderon said their interest in Ronaldo was over but added that it was "sad a professional with Ferguson's career can make such declarations."
David Beckham, Ruud van Nistelrooy and Gabriel Heinze have all previously made the journey from Old Trafford to Madrid, but Real's persistent comments about Ronaldo seem to have made Ferguson more determined than ever to hold on to the Portuguese player.
When asked about the matter at the Club World Cup in Japan, Ferguson said: "Would I get into a contract with that mob? Absolutely no chance"
"I wouldn't sell them a virus - that's a no. There's no agreement whatsoever between the clubs.
Over the five years he has been with us, we have seen him develop into the player he is today
Sir Alex Ferguson on Cristiano Ronaldo
"I said to David Gill a year last summer, when we sold Gabby Heinze, you can bet your life in January it will all start up with Ronaldo again. It'll happen again this January, believe me.
"We've just got to ignore it because if we keep worrying about what Real are going to say then we are not going to concentrate on our own programme of difficult games coming up.
"Sometimes it can be an angry situation and sometimes we are really annoyed with them, but we know the game and I think we should just play our game and ignore it all."
Ronaldo has also responded to the claims saying he is happy to stay at Old Trafford and is unaware of Real's reported interest.
"I don't care. I don't see newspapers," he said. "We are out here in Japan and I don't know nothing, what's happened around me.
"I am very happy (at Man Utd), very happy."
Previously Trapote, who is understood to be very close to Calderon, had told Spanish newspaper El Mundo: "We have already signed our top target for next summer.
"Is it Cristiano Ronaldo? It is Cristiano, there is no-one else. The thing is, it is better not to say anything right now."
The latest twist in the Real Madrid-Ronaldo story could well open wounds between the clubs following the acrimonious dealings between United and the Spanish giants over the summer.
Real's public pursuit of the 23-year-old ended with United complaining to Fifa over their conduct, with Ferguson claiming they had shown "a lack of morals".
The case was dismissed because of a lack of evidence, and Ronaldo later told Spanish sports paper Marca in October that he is "with Manchester in body and soul".
Ronaldo, this year's Ballon D'Or winner, is currently contracted at Old Trafford until 2012 and Ferguson has been delighted with his improvement since arriving at Old Trafford as a raw teenager in 2003.
"Over the five years he has been with us, we have seen him develop into the player he is today," he added.
"He always had certain attributes that pointed him towards the very top - his amazing skill, his speed and his courage. In the time he has been with us, he has developed his decision-making.
"As a kid he played centre-forward for Sporting Lisbon and our people in Portugal kept telling us that 'this boy is a great goalscorer.'
"When he first came to us, we couldn't see that. All of a sudden he just blossomed and last season he got 42.
"That is a measure of a young person wanting to do well, to improve himself by his own determination and ambition to practise all the time."
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