I wasn't thinking about emails: Clinton

Hillary Clinton says her use of a private email system at the State Department wasn't the "best choice" and she's acknowledged 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 on Friday said in an interview 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," Clinton said in the rare extended interview.

"There was so much work to be done. We had so many problems around the world.

"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 judgment.

"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 have criticised Clinton's unwillingness to apologise saying it underscores polls which have shown large numbers of people question 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 spokesman for the Republican National Committee.