WASHINGTON — As criticism mounted on the Obama administration, Secretary of State Hillary Rodham Clinton acted Monday to shield the president from blame for the deadly September attack on a U.S. mission in Libya, saying that any fault lies with her as America’s top diplomat.

“I take responsibility,” Clinton told a CNN interviewer during a trip to Peru.

U.S. Ambassador J. Christopher Stevens and three other Americans were killed Sept. 11 when dozens of heavily armed men drove up in a convoy and attacked and burned the thinly protected U.S. diplomatic mission and a nearby annex in Benghazi.

Two State Department security officers who served in Libya this year told a House oversight hearing last week that they had requested an extension of a 16-member military team at the U.S. Embassy in Tripoli, several hundred miles away from Benghazi, but that mid-level State Department officers in Washington had rejected the request.

In addition to the congressional probe, the State Department has convened a formal review of the assault, and the FBI has sent agents to Libya to conduct a criminal investigation.

Though the incident could mar Clinton’s record as chief diplomat, Republicans in Congress and on the campaign trail have raised few questions about her role. They have charged instead that the failure to protect the diplomatic mission reflects a broader failure of foreign policy by Obama as he runs for re-election.

Clinton has kept a generally low profile on the issue and on Friday she declined to answer a reporter’s question about precisely what she was doing during the attack.

On Monday, Clinton portrayed the mounting criticism as motivated by political partisanship. “I want to avoid some kind of political gotcha,” she said.

She said Obama and Vice President Joe Biden were not involved in decisions about the level of security for diplomats in Libya, a country that has been overflowing with weapons since an armed insurgency toppled and killed former leader Moammar Gadhafi last year.

At the vice presidential debate last Thursday, Biden said that “we didn’t know” of any requests for beefed-up security. After GOP presidential nominee Mitt Romney accused Biden the next day of hiding the truth, administration officials clarified that the request was handled by mid-level officials at the State Department, not the White House.

Clinton defended the administration’s early misstatements about the Benghazi incident, citing “confusion” about the attackers’ motives. Embassy employees, including a sizable CIA team, were evacuated from Benghazi immediately after the attack, and the FBI was not allowed to inspect the burned-out mission for nearly three weeks.

Administration officials, including U.S. Ambassador to the United Nations Susan Rice, initially said they believed the attack was a spontaneous explosion of anger over an anti-Islamic video made in California. They now describe the assault as a coordinated attack involving at least some extremists from groups linked to al-Qaida.