Ronaldo is set to join Real Madrid in a £80million deal at the end of this month.
The former Sporting Lisbon ace insisted in May that United was where he wanted to stay.
Ronaldo told News of the World: “After we won the European Cup I thought there is no more I can achieve here. And when you have done all you can, you know it is time for a new challenge. I stayed one more season and it was nice to make it three titles in a row but it was my dream to play for Madrid.”
He added: “Anything that has not been right with the move is my fault and nothing to do with Real Madrid or Manchester United. I opened my mouth and that is what caused the problems between the two clubs who both acted in the correct way. Yes, I would have handled things differently and not been so public.”