U.S. President Barack Obama assumed responsibility for the deadly terror attack in Libya last month that killed four Americans just hours after Secretary of State Hillary Clinton sought to shoulder the blame for any mistakes the administration made, The Associated Press reports.

"She works for me," the President said in New York in his second presidential debate with Republican challenger Mitt Romney. "I'm the president and I'm always responsible, and that's why nobody's more interested in finding out exactly what happened than I do."

With three weeks before the presidential election, the administration has been unable to put to rest its handling of the Benghazi attack that killed Ambassador Chris Stevens, a State Department computer specialist and two former Navy SEALs who were working as contract security guards.

Obama's statement came amid a spirited back-and-forth with the former Massachusetts governor over the administration's handling of the Benghazi attack, the only significant foreign policy disagreement in an hour-and-a-half exchange dominated by domestic concerns.

Romney challenged the President to explain why U.S officials argued for more than a week after the Sept 11 assault that it stemmed from a protest against an American-made film ridiculing Islam.

"Whether there was some misleading, or instead whether we just didn't know what happened, you have to ask yourself why didn't we know," Romney said. "It was very clear this was not a demonstration," he said. "This was an attack by terrorists."