Sergio Alves, who claims to be a representative of the winger, told Barcelona radio station Onda Cera: "When Real and Barca are involved the future is always open, not closed.
"Given a little bit of time, the situation may change, let's see."
Ronaldo's future in England looked bleak after he was made a scapegoat for England's World Cup exit to Portugal in the summer, winking in the direction of the Portugal bench after Wayne Rooney's dismissal.
He overcame the early-season taunts to find his best form to date for United and is currently the second-highest goalscorer in the Premiership with 13 goals.
Barcelona manager Frank Rijkaard;
"Without a doubt, he is one of the most valuable players in world football. But there are only rumours at the moment, there is nothing concrete. I must say that yes, he is a great player, but we cannot do anything else at this moment. It is still too soon to comment on future signings. We still have many games to play and this group has much to demonstrate."
"I would like to have Cristiano here in Barcelona.
"He has great talent and is still very young, but it seems unlikely he would leave Manchester in their current position."
"I know of the interest of Real Madrid, but I can not say anything.
"I have had two conversations with Carlos Queiroz and Alex Ferguson and they have forbidden me to speak about Real Madrid.
"You have to understand that because I don't want any problems."