WASHINGTON - US Secretary of State Hillary Clinton said on Monday that she took responsibility for the deadly assault on the American consulate in Benghazi, in an apparent bid to take the heat off President Barack Obama who is now under heavy criticism.

"I take responsibility" for the protection of US diplomats, Clinton told CNN during her visit to Lima, Peru. But she said an investigation now under way will ultimately determine what happened in the attacks on the consulate.

"I'm in charge of the State Department -- 60,000 plus people all over the world, 275 posts," she said in the CNN interview, just one day before the second presidential debate between Obama and his Republican rival Mitt Romney.

"The president and the vice-president certainly wouldn't be knowledgeable about specific decisions that are made by security professionals," she said.

The attacks on the US consulate in Benghazi on the night of Sept 11, which resulted in the deaths of US Ambassador to Libya Christopher Stevens and three of his staff, shocked the United States.

The Obama administration has been under fire after Vice-President Joe Biden said in the vice-presidential debate that he was not aware of requests for more security at the Benghazi consulate, in contradiction with testimony by former US security officers in Libya that such requests have been made and turned down.

The White House later defended Biden's statement, saying that he did not know of the requests because such decisions are made by the State Department.

"I want to avoid some kind of political gotcha," said Clinton, insisting that Obama and Biden are not involved in security decisions related to the consulate.

Clinton also sought to downplay the criticism that the Obama administration initially said the assault was a spontaneous result of a protest over an anti-Islam film.

There is always "confusion" in the wake of an attack, she said.