US Secretary of State Hillary Clinton says she takes responsibility for the security failure at the Benghazi consulate that led to the killing of four Americans in Libya last month.
Mrs Clinton said ensuring the safety of US diplomatic staff overseas was her job, not that of the White House.
US Republicans have strongly criticised President Barack Obama over the attack.
And Republican challenger Mitt Romney is likely to raise it again in the second campaign debate with Mr Obama.
"I take responsibility," Mrs Clinton told CNN. "I'm in charge of the state department's 60,000-plus people all over the world [at] 275 posts."
It seems Mrs Clinton is trying to draw criticism away from Mr Obama, who needs a strong debate performance if he is to recover his lead in the polls, says the BBC's Adam Brookes in Washington.
In her interviews with US TV channels, Mrs Clinton appeared to acknowledge that she was trying to shield the president, our correspondent says.
"What we had to do in the state department was keep focused not on why something happened - that was for the intelligence community to determine - but what was happening and what could happen," Mrs Clinton said.
"And that's what I was very much working on, day and night, to try to make sure that we intervened with governments. We did everything we could to keep our people safe, which is my primary responsibility."
Mrs Clinton said she was focused on tracking down the killers of the US ambassador to Libya and bringing them to justice.
"I don't think we want to get into any blame game. I think what we want to do is get to the bottom of what happened, figure out what we're going to do to protect people and prevent it from happening again and then track down whoever did and bring them to justice."
Last week, a US congressional committee heard US security in Libya was reduced before the attack on the US consulate, even as violence worsened.
Mr Romney has been making the Benghazi attack the centrepiece of his case against President Obama's foreign policy, and has accused Vice-President Joe Biden of making misleading statements about the attack.
Mr Romney said Mr Biden's statement in the recent vice-presidential debate that the administration was not told about requests for extra security in Libya contradicted the sworn testimony of state department officials.
Mrs Clinton backed up Mr Biden's assertion: "The president and the vice-president wouldn't be knowledgeable about specific decisions that are made by security professionals."
A congressional panel has already heard there had been repeated requests to the state department for beefed-up security at the diplomatic compound.
In the days after the attack, Mr Obama's ambassador to the United Nations, Susan Rice, described it as a "spontaneous" assault that arose out of a protest against a US-made amateur video which mocks Islam.
But US officials have since said the government had never concluded the attack was motivated by the film.
Mr Obama and Mr Romney are preparing to face off in their second debate later on Tuesday, at Hofstra University in Hempstead, New York.
Mr Romney was widely acknowledged as having the upper hand in the first debate, which was reflected in the opinion polls, with many showing Mr Romney in the lead for the first time in the campaign.
Ambassador Christopher Stevens died of smoke inhalation when he was trapped alone in the burning consulate building on 11 September. Three other officials were killed, and three wounded.
Earlier this week, the father of Ambassador Stevens said it would be "abhorrent" to turn his son's death into a campaign issue.
"Our position is it would be a real shame if this were politicised," Jan Stevens said.