NEW YORK -- Donny Osmond has apologized to Larry King for criticizing the CNN talk-show host after he revealed that Marie Osmond's 16-year-old son had entered rehab.

"I was very upset about it," the 49-year-old singer said in an interview that aired Monday on NBC's "Today" show. "I thought it was very unfair for Larry King to throw that question at Marie the way he did."

Donny Osmond and his sister, who starred on television's "Donny and Marie Show" during the 1970s, appeared stunned when King asked about Michael in an interview last week.

Osmond said he later learned the tabloids were about to break the story.

"I have to back up and apologize publicly to Larry King because I came out and said some things against him," he said.

"... In hindsight, Larry King did Marie a favor," Osmond said. "She was able to make a statement about the situation. ... And so she's grateful to Larry."

Marie Osmond, who is competing on ABC's "Dancing With the Stars," hasn't disclosed the nature of Michael's problem or where he is being treated.

Osmond, 48, announced earlier this year that she and her second husband, Brian Blosil, are divorcing. She has eight children.