Hillary Clinton
Hillary ClintonReuters

Democratic presidential front-runner Hillary Clinton on Tuesday said she is "sorry" for using a private email server during her time as Secretary of State, CNN reported.

Clinton was going further than ever before to express remorse for the controversy that has rocked her campaign, the network noted.

"I'm sorry about that," Clinton said in an at-times emotional interview on ABC News, acknowledging that she should have used separate accounts for work and personal business. "I take responsibility and I am trying to be as transparent as I possibly can."

She later went even further and issued a slightly different apology, saying she was "sorry that it has raised all these questions."

Clinton is facing criticism for having used a personal email address during her entire four years as secretary of state, despite the fact that under specific guidelines signed into law by President Barack Obama, government email accounts are supposed to be used in any situation involving official business.

Clinton has said she used private emails out of "convenience", though she has also admitted it "would have been better" to have two accounts to separate work and personal emails. An internal government review has found that she sent at least four emails from her personal account containing classified information during her time heading the State Department.

Though she has taken responsibility for her exclusive use of a private email server during her time as secretary of state, she told The Associated Press on Monday that she doesn't need to apologize for her nagging email controversy because "what I did was allowed."

Clinton defended her practices again on ABC, saying that everyone she emailed in the White House and Obama administration knew she used a private account.

She also disputed that she ever traded information over email that was marked classified at the time, according to the CNN report.

The Democratic front-runner got choked up at one point, when speaking of her late mother and how hard it is to campaign "24/7."

"It's something that just demands everything -- physically, emotionally, spiritually," she was quoted as having said. "I can have a perfectly fine life not being president."

Clinton also offered praise for potential rival Vice President Joe Biden, who is mulling a 2016 bid.

"I think he could be a good president, there's no doubt about that," she said, according to CNN.

Clinton turned over 55,000 pages of emails to the State Department earlier this year, but the email controversy has not gone away, partly because of a congressional inquiry into the terrorist attacks in Benghazi has also focused on Clinton's email set up.