Libero says United will sign Ronaldo this summer with the Real Madrid superstar unsettled at the Bernabeu.
Paris Saint-Germain are also competing for the Portuguese's signature.
The 33-year-old hit a hat-trick for the Selecao against Spain to underline his credentials on the world stage.
But immediately after the Champions League final, Ronaldo threw his future into doubt and a return to Old Trafford appears to now be on the cards.
PSG remain an intriguing option, even if the presence of Neymar makes a deal more complicated.