I have regretted it for 33 years, of course I regret it," the Franco-Polish filmmaker told Swiss television channel TSR, or Television suisse-romande.
Polanski pleaded guilty to having unlawful intercourse with the 13-year-old girl after plying her with drugs and champagne in 1977.
He was initially charged with six felony counts, including rape and sodomy, but the charges were later reduced under a plea deal made in part to spare the teen the ordeal of a trial.
Polanski later served 42 days at a secure unit undergoing psychiatric evaluation but fled the United States on the eve of his sentencing in 1978 amid fears the trial judge planned to go back on a previously agreed plea deal.
His flight from justice came after a string of hit films including "Rosemary's Baby" and "Chinatown".
The director, whose pregnant wife Sharon Tate was horrifically murdered by Charles Manson's "family" in 1969, won an Oscar for his 2002 film "The Pianist" but was unable to collect the award because of his fugitive status.
The filmmaker was then arrested on an international warrant over the decades-old child sex case on September 27, 2009, upon his arrival at the airport in Zurich, as he was headed to the city's film festival.
Polanski spent 10 months in Swiss custody before convincing the authorities in Bern not to honour a US extradition request, and instead to release him.
In the interview, he also recalled his traumatic past as a Jewish child in a Polish ghetto during World War II and Tate's murder, saying he was "made of stronger stuff."
"I am used to death a little bit like surgeons are used to seeing a stomach cut open," he said.
Recalling Tate's murder, he said: "At the beginning, the suspicions fell on me before Charles Manson's arrest because I had directed 'Rosemary's Baby.'"
The 1968 horror film tells the story of a young mother who becomes mysteriously pregnant and is then taken over by paranoia over the safety of her unborn child.