The Portuguese superstar wants Jorge Mendes to “do everything possible” to make the move happen.
Ronaldo, who left Old Trafford for Real Madrid eight years ago, stunned the Spanish giants when his desire to leave emerged on Friday.
The forward faces allegations of a £13million tax fraud and now doubts over his Real future have sparked a megabucks scramble for his services.
United, Chelsea, Paris Saint-Germain and Bayern Munich are all potential suitors.
PSG are prepared to offer £122m to land him plus a staggering salary of £26m per year to persuade him to switch to the French capital.
But Ronaldo is keen to return to United and has instructed his representative, fellow Portuguese and super-agent Mendes, to do everything in his power to make it reality.
The 32-year-old is understood to feel he had unfinished business at Old Trafford and cannot miss out on the chance to return as a hero.