Katie Couric and Stephen Collins Katie Couric and Stephen Collins

Earlier this week, Stephen Collins publicly admitted that he had molested three underage girls between the 1970s and 1990s. But the 7th Heaven star insists to Katie Couric that he isn't a pedophile.

"I do not fit either the clinical or dictionary definition of it," Collins says in a preview of his 20/20 sit-down with Couric. "A pedophile is someone who is mainly or wholly attracted to children. I'm not. I had a distortion in my thinking where I acted out in those ways, but I'm absolutely not attracted physically or sexually attracted to children. I'm just not."

Collins adds that a therapist also told him that he did not exhibit the hallmarks of a pedophile. "I remember talking about this once with a therapist and the therapist assuring me these incidents were such that... someone with that attraction would've acted many more times. They were terrible, and I regret them deeply, but I don't look at young women that way. I don't. And I never did," Collins continues. "That may sound incongruous with those actions, but those actions, I think, had more to do with that distortion in my thinking and need for attention — it was not a desire to be in any way in sexual contact with them.

Stephen Collins admits to molesting underage girls

"And that's why I say in that moment in '73 when that physical contact took place, it was the end, if there had been anything desirous up until then, that ended it. That stopped it. It was the opposite of excitement or gratification," he says.

In regards to the report that he is attracted to young boys, Collins said that is just a rumor fabricated by his estranged wife, Faye Grant. "It too leaves me speechless," he told Couric.

Collins' full interview with Couric will air on 20/20 Friday on ABC. Watch a clip below.