WASHINGTON - Hillary Rodham Clinton says her use of a private email account was a "mistake," adding that she is "sorry" and takes responsibility for the decision.

Clinton offers the apology in an interview with ABC News on Tuesday after declining to do so previously. On Friday, she didn't apologize for using a private email system when asked directly by NBC News.

In an interview with The Associated Press on Monday, she said an apology wasn't necessary because what she did was "allowed" by the State Department.

The Democratic presidential candidate tells ABC News her email set-up "was a mistake. I'm sorry about that. I take responsibility and I'm trying to be as transparent as I possibly can."

Clinton's campaign has struggled against scrutiny of her use of a private email system.