In an interview on Brazil's Globo TV, the AC Milan striker on Sunday denied claims by one of the prostitutes that he had sex with them and used drugs, but admitted that the incident will haunt the rest of his career.

"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."

In a halting voice, 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 plays for Italian club AC Milan but 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.

"I made the stupidest mistake ever of my personal life," he said. "Anyone can make a mistake, and I made a big mistake."