Arnold Schwarzenegger Tells '60 Minutes' Affair was the 'Stupidest Thing I've Done' (Video)

It was "the stupidest thing" he's done.

That's how Arnold Schwarzenegger describes his affair with the family housekeeper that led to the birth of an illegitimate son -- and the end of his 25-year marriage to Maria Shriver -- in a new 60 Minutes interview.

VIDEO: Arnold Schwarzenegger Releases Trailer for New Memoir 

In a preview released online on Friday, Schwarzenegger, who is currently promoting his new memoir Total Recall: My Unbelievably True Life Story, faces some tough questions from Lesley Stahl.

"So you lied to her," Stahl says.

"You could say that," Schwarzenegger replies.

STORY: Arnold Schwarzenegger's Book Recounts How Maria Shriver Confronted Him About His Love Child 

"She gave up her television career for you. I mean wow. Was this just the most unbelievable act of betrayal to Maria?" the interviewer presses on.

Schwarzenegger admits that it is, saying, "I think it was the stupidest thing I have done in the whole relationship. ... I inflicted unbelievable pain on Maria and the kids." The book goes into detail about how the affair came out, with Shriver confronting her husband with it at a couples' counseling session.

The full interview airs on 60 Minutes' season premiere, airing Sunday, Sept. 30 at 7:00 p.m. ET/PT.