Hillary Rodham Clinton said her use of a private email system at the State Department was not the "best choice" and acknowledged that she didn't "stop and think" about her email set-up when she became President Barack Obama's secretary of state in 2009.
The Democratic presidential front-runner said in an interview, on Friday, with NBC News that she was immediately confronted by a number of global hotspots after joining the new Obama administration as its top diplomat and didn't think much about her email after arriving at her new job. Her use of private email has now become a distraction for her presidential campaign.
"You know, I was not thinking a lot when I got in. There was so much work to be done. We had so many problems around the world," Clinton said. "I didn't really stop and think what kind of email system will there be."
But Clinton did not apologise for her decision when asked directly, "Are you sorry?"
Instead, she again said she wishes she had "made a different choice" and that she takes responsibility for the decision to use a private email account and server based at her home in suburban New York.
She added it was a choice that should not raise questions about her judgement.
"I am very confident that by the time this campaign has run its course, people will know that what I've been saying is accurate," Clinton said, adding: "They may disagree, as I now disagree, with the choice that I made. But the facts that I have put forth have remained the same."
Republicans criticised Clinton's unwillingness to apologise for the decision and said it underscored polls which have shown large numbers of people questioning her trustworthiness.
"What's clear is Hillary Clinton regrets that she got caught and is paying a political price, not the fact her secret email server put our national security at risk," said Michael Short, a spokesperson for the Republican National Committee.
The Washington Post reported on Friday that the Clintons personally paid a State Department employee, Bryan Pagliano, to maintain the private email server she used while secretary of state.
Earlier this week Pagliano told a House committee investigating Clinton's use of the email server that he would invoke his Fifth Amendment constitutional right against self-incrimination if called to testify.
The subject of emails led off a wide-ranging interview that included vice-president Joe Biden's interest in a potential Democratic primary bid, Clinton's plans to address the Iran nuclear deal and her views of Republican front-runner Donald Trump.
Following a summer in which both Trump and senator Bernie Sanders, a longshot rival for the Democratic nomination, drew large campaign audiences, Clinton sought to cast her candidacy as one rooted in tackling the problems "that keep families up at night".
Clinton's interview comes as current and former aides are testifying before a congressional panel investigating the deadly 2012 Benghazi attacks. The committee has also delved into Clinton's email practices at the State Department. She is scheduled to testify publicly before the panel next month.
In August, Clinton had handed over her private server to the FBI, which she used to send, receive and store emails during her four years as the secretary of state. Clinton said she had set up her own system instead of using a State Department account for the convenience of using a single Blackberry device.
But her comments that she did not stop to think about setting up a private email server in her home belied the careful planning and technical sophistication required to operate, maintain and protect a private server effectively -- especially one responsible for the confidential communication of the US government's top diplomat as she travelled the globe.
Even homebrew servers typically require careful configuration, internet registration, data backups, regular security audits and a secondary power supply in case of electrical problems.
In the interview, Clinton said, as she has in the past, that she "should have had two accounts, one for personal and one for work-related".
Thousands of pages of her emails publicly released in recent months have shown that Clinton received messages that were later determined to contain classified information, including some that contained material regarding the production and dissemination of US intelligence.
But Clinton reiterated that she did not "send or receive any material marked classified. We dealt with classified material on a totally different system. I dealt with it in person".
Clinton noted her support for an Obama-backed agreement to curb Iran's nuclear ambitions and said she would address what she would do as president to enforce the deal, hold Iran accountable and "make clear that no options were off the table. That they can never ever have a nuclear weapon".
Clinton suggested that Trump, the leading Republican candidate at this juncture, did not have the temperament to lead the nation and conduct foreign policy. "Loose talk, threats, insults, they have consequences. So I'm going to conduct myself as I believe is appropriate for someone seeking the highest office in our country," she said.