United's bitter rivals City were hoping to capitalise this and were believed to be plotting a double transfer swoop worth £134m Ronaldo and his team-mate Fabio Coentrao last month.
And PSG director Leonardo has admitted he is still open to the idea of Ronaldo joining the club.
He told L'Equipe: "Cristiano Ronaldo? Paris Saint-Germain have become a club where anything is possible.
"When we are discussing a possible transfer for a player like Cristiano Ronaldo, there are only four or five clubs that can be taken into consideration. Paris Saint-Germain are one of those clubs."
Ronaldo hit another hat-trick for Real earlier this week in their 4-0 thrashing of Celta Vigo in the Copa del Rey to take his tally for the season to 28.