Ronaldo was heavily linked with a move to Real Madrid last summer
Manchester United have accepted a world record offer of £80m from Real Madrid for Cristiano Ronaldo.
"United have agreed to give Real Madrid permission to talk to the player," said a statement from the English club.
It added that the decision came at Ronaldo's request after he "again expressed his desire to leave".
United described the offer for the 24-year-old forward as unconditional and added that they expected the matter to be concluded by 30 June.
It is understood that the transfer fee would be made available for manager Sir Alex Ferguson to invest in the transfer market.
Madrid signed Brazilian Kaka for a reported £56m earlier in the week, surpassing the previous world record fee of £45.6m Real paid for Zinedine Zidane in 2001.
That deal was sealed by the ambition of returning Real president Florentino Perez, who previously led the Spanish club from 2000 to 2006 - during the famous galacticos era.
And Perez had earlier made it clear that he would do "everything possible" to sign Ronaldo.
Madrid have also been linked with Liverpool's Xabi Alonso, Valencia's David Villa and Bayern Munich's Franck Ribery since Perez's unopposed election signalled the return of their vast spending.
Ronaldo, who joined United in 2003 from Sporting Lisbon for £12.2m, was strongly linked with a move to the Spanish capital last summer.
United lodged a complaint with world governing body Fifa last June over what they believed was a deliberate attempt by Real to unsettle the winger.
After a long drawn out saga that ran through the summer months the Portugal international remained at United for the 2008-09 season.
"Now I understand I made the best decision," Ronaldo told Spanish sports paper Marca at the end of last summer. "I am with Manchester in body and soul.
But the speculation soured relations between the clubs and last December United manager Sir Alex Ferguson said that he would not "sell that mob a virus".
And despite Ronaldo's claim that he wanted to remain at Old Trafford he was the subject of constant speculation during the 2008-09 season and often gave mixed messages about his future.
If Ronaldo does sign for Madrid his last appearance for United would have been in the Champions League final that the Premier League champions lost 2-0 to Barcelona in Rome.
After the final Ronaldo was critical of Ferguson's tactics.
Manchester United have accepted a world record offer of £80m from Real Madrid for Cristiano Ronaldo.
"United have agreed to give Real Madrid permission to talk to the player," said a statement from the English club.
It added that the decision came at Ronaldo's request after he "again expressed his desire to leave".
United described the offer for the 24-year-old forward as unconditional and added that they expected the matter to be concluded by 30 June.
It is understood that the transfer fee would be made available for manager Sir Alex Ferguson to invest in the transfer market.
Madrid signed Brazilian Kaka for a reported £56m earlier in the week, surpassing the previous world record fee of £45.6m Real paid for Zinedine Zidane in 2001.
That deal was sealed by the ambition of returning Real president Florentino Perez, who previously led the Spanish club from 2000 to 2006 - during the famous galacticos era.
And Perez had earlier made it clear that he would do "everything possible" to sign Ronaldo.
Madrid have also been linked with Liverpool's Xabi Alonso, Valencia's David Villa and Bayern Munich's Franck Ribery since Perez's unopposed election signalled the return of their vast spending.
Ronaldo, who joined United in 2003 from Sporting Lisbon for £12.2m, was strongly linked with a move to the Spanish capital last summer.
United lodged a complaint with world governing body Fifa last June over what they believed was a deliberate attempt by Real to unsettle the winger.
After a long drawn out saga that ran through the summer months the Portugal international remained at United for the 2008-09 season.
"Now I understand I made the best decision," Ronaldo told Spanish sports paper Marca at the end of last summer. "I am with Manchester in body and soul.
But the speculation soured relations between the clubs and last December United manager Sir Alex Ferguson said that he would not "sell that mob a virus".
And despite Ronaldo's claim that he wanted to remain at Old Trafford he was the subject of constant speculation during the 2008-09 season and often gave mixed messages about his future.
If Ronaldo does sign for Madrid his last appearance for United would have been in the Champions League final that the Premier League champions lost 2-0 to Barcelona in Rome.
After the final Ronaldo was critical of Ferguson's tactics.
