The Portugal international has three years left on his current £120,000-a-week contract and according to FIFA rules he can buy himself out of his contract at the end of next season.
United are ready to offer him a new £150,000-a-week contract to stop him joining Spanish giants Real Madrid.
United boss Sir Alex Ferguson said: “Next summer will be a key element of his contract situation — he will have three years left then.
“Nobody (at Manchester United) has ever bought himself out of his contract. I don’t think it will be an issue.”
Fergie added: “There is no question of Ronaldo leaving.
“Calderon promised everyone they would get the lad in the summer. There was a complete arrogance about it. So I was delighted Ronaldo stayed.
“We are ready for more shots. We have enough ammunition ready.”
