Former U.S. Secretary of State Hillary Clinton opens up on what her critics have described as her achilles heel: Benghazi. Appearing at the National Automobile Dealers Association meeting in New Orleans, Clinton called the attack her biggest regret. (Reuters)

Hillary Clinton said Monday that the deaths of four Americans in Benghazi, Libya, are her biggest regret during her tenure as secretary of state.

"My biggest, you know, regret is what happened in Benghazi," Clinton said during remarks at the National Automobile Dealers Association conference in New Orleans. "It was a terrible tragedy losing four Americans -- two diplomats and, now it's public so I can say, two CIA operatives."

Clinton was quick to note, though, that people in her position have to make decisions based upon imperfect information.

"But that doesn’t mean that there isn't going to be unforeseen consequences, unpredictable twists and turns," she said.

Republicans have relentlessly criticized Clinton for what happened in Benghazi and what they see as a lack of accountability on her part. During Congressional hearings into the matter, Republicans pressed Clinton on the incorrect talking points the administration used in the weeks after the attacks, to which Clinton exclaimed: "What difference, at this point, does it make?"

The matter looms over Clinton's potential 2016 presidential campaign.