There was speculation that a deal could see Michael Carrick return to White Hart Lane in exchange for Modric but Redknapp insists there is no truth in the story.
"I want to keep Luka here and I am sure Alex wants to keep Michael at Man Utd, so that's a load of rubbish.
"He (Ferguson) likes him (Modric) but I like Ronaldo. I couldn't get him. It's never going to happen. Alex has never made an approach for him."
Redknapp also confirmed that he would not be trying to sign keeper David James from Portsmouth.
"There is nothing in that one," he stressed. "That is just another rumour."
However, Redknapp does not believe there is any chance of the England international making the move across London
"Any team would like Joe but he is not a player I have even made a phone call about because I don't think it would be possible to get him. He belongs to Chelsea."