In an interview with Portuguese newspaper Publico, the 23-year-old confirmed he would like to play in Spain one day but that he is currently satisfied with life in England.
"There is nothing certain at the moment," Ronaldo said. "The press always make stories about interest from other teams, not only from Madrid, also from Barcelona.
"On one hand it's good and means that they know your value as a player and think you can be a good reinforcement for other teams.
"But my head is in Manchester because it is the club that, at the moment, puts me in the best condition and that I'm happy at.
"Now, as I have said many times, only God knows the future.
"I have never hid from anyone that I would like to play in Spain one day. It's a dream, but sometimes dreams don't happen.
"I can guarantee that I am happy at Manchester United and that I would love to continue."