Cristiano Ronaldo admits it would be incredibly difficult to sign for Manchester City given his allegiances to Manchester United but, says the Real Madrid superstar, a transfer Etihad Stadium would not be 'impossible'.

The Portugal captain meets Manchester United on Wednesday evening for the first time since his world record transfer to the Santiago Bernabeu in the summer of 2009, and the Champions League encounter is likely to be an emotional experience.

Ronaldo is still fondly regarded by fans and players alike at Manchester United and, at the start of this season, had been linked with a move back to Old Trafford after reports emerged claiming he was unhappy with life at Real Madrid.

The 28-year-old, though, has refuted suggestions that he wants to leave Real Madrid, but adds that is not willing to rule out an eventual return to Manchester United.

"I am a player of Real Madrid and I’m happy here, my family is happy and everything is going well for me here. The future? I don’t know — only God knows the future," Ronaldo told The Sun.

"I can’t say I’m never going back to Man United — but I can say I’m good here and I want to be here. Let’s leave it at that and see what God gives me in the future — but I repeat I am happy here."

But what about eventually leaving Real Madrid for Manchester City? It is something Ronaldo would be loath to do but, admits the Portuguese, nothing in football is beyond the realms of possibility.

"I’m not going to say it is impossible, because in football the impossible doesn’t exist," he added.

"But I can say it would be very, very, very, very, very, very, very, very, very, very, very, very difficult to play at Man City. VERY difficult because of Manchester United."

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