"It was an isolated and stupid act," the three-time FIFA Player of the Year said on Globo's hugely popular "Fantastico" program. "I'm sorry and ashamed."
Ronaldo said he wasn't aware the prostitutes were cross-dressers until he got to a motel with them, discovered they were men and decided not to have sex with them because he is heterosexual.
Ronaldo, who is recovering from knee surgery in Brazil, also said he had been drinking earlier that night after watching Rio's Flamengo win against rival Botafogo - but was not drunk.
He also said: "Going to that place, I realised they were transvestites and tried to finish it there, so I could get back home. I was already sorry, of course, to have made that choice. But I could not get out, because the whole extortion began.
"I feel very ashamed speaking about this matter. It was an isolated act, an act of complete stupidity on my part. I never knew what a transvestite was. I am completely heterosexual.
"My error has created a major problem of global impact. But thank God all the facts are coming to light. I've spoken to my attorney and everything is being investigated and will be proven.
"Certainly this will tarnish my personal life forever. But it will not interfere in my position as ambassador for Unicef. And this will not interfere also in the advertising contracts I have. This is an isolated act that will not happen again."
Ronaldo also admitted his time at AC Milan is all but over.
"My contract with Milan expires in June and from there I will be free to negotiate with anyone. This already is more or less mapped out.
"It will be my great dream and I am sure that the doors are open for me to return to Flamengo."