New York, Sep 29 (IANS): Actor Arnold Schwarzenegger has opened up about his marriage breakdown for the first time and admits he has hurt ex-wife Maria Shriver by cheating on her.

The 65-year-old admits that cheating on wife Maria Shriver with housekeeper Mildred Baena was the "stupidest thing" he had done, reports people.com.

"I think it was the stupidest thing I've done in the whole relationship. It was terrible. I inflicted tremendous pain on Maria and unbelievable pain on the kids," Schwarzenegger said on a TV show while promoting his book "In Total Recall: My Unbelievably True Life Story".

In the book, Hollywood action star writes about the affair with Baena and having a son with her named Joseph, now a teenager, and reveals another affair during his 25-year marriage.

However, he says Shriver, who filed for divorce in May 2011, has not read the book.

"She knows that it's about my whole life and that I would not write a book and kind of leave out that part and make people feel like, 'Well, wait a minute. Are we just getting a book about his success stories and not talk about his failures?. I wanted to write a book about me," he said.