According to The Sun, Ronaldo has declined an offer from Real for signing a new contract.
He has two years left on his current agreement and is understood to be interested in making the move back to United.
United plans to offer upto 65 million pounds and a player to Real in exchange for Ronaldo.
If the terms are agreed to, this will make Ronaldo joint top earner with Wayne Rooney at 250,000-pounds-a-week.
According to the report, Ronaldo has not always been content at Santiago Bernabeu, and is reported to be missing the company of many of his old team-mates at United.
He has also expressed his disappointment over the retirement of United manager Alex Ferguson.