Washington (CNN) -- Last September's terrorist attack in Libya that killed the U.S. ambassador and three other Americans didn't happen in a vacuum but was part of a "broader strategic challenge in North Africa and the wider region," Secretary of State Hillary Clinton said Wednesday.
In sometimes emotional testimony before the Senate Foreign Relations Committee on the September 11 attack on a diplomatic compound in Benghazi, Clinton reiterated that her position made her responsible for what happened.
"As I have said many times since September 11, I take responsibility," Clinton told the panel.
In response to critics who have charged that the State Department refused additional protection sought by diplomatic and security staff, Clinton said in opening remarks that there was "timely" and "exceptional" coordination between the State Department and the Pentagon on the night of the attack
"No delays in decision-making. No denials of support from Washington or from the military,' Clinton said. An independent review of the U.S. government's response to the attack, she noted, "said our response saved American lives in real time -- and it did."
Clinton said she directed the response to the attack from the State Department that night and "stayed in close contact with officials from across our government and the Libyan government."
Anticipating criticism of misleading "talking points" prepared by the CIA that initially said the attack on the mission was motivated by anger over an anti-Islam video, Clinton said: "The very next morning, I told the American people that 'heavily armed militants assaulted our compound' and vowed to bring them to justice. And I stood with President Obama as he spoke of 'an act of terror.' "
In addition, Clinton said she immediately took steps to beef up security at U.S. posts around the world, including creating an independent review board that found "systematic failures" in how the State Department handled security at the mission.
"I have accepted every one of their recommendations," she said. "I asked the deputy secretary for management and resources to lead a task force to ensure that all 29 of them are implemented quickly and completely as well as pursuing additional steps above and beyond the recommendations."
The appearance in the Senate and, later Wednesday, before a House committee, was one of the last acts for Clinton before she leaves her post as long planned.
"For me, this is not just a matter of policy," she said. "It's personal."
In reference to the return of remains of Ambassador Christopher Stevens and the other three slain Americans, Clinton said in voice choked with emotion: "I stood next to President Obama as the Marines carried those flag-draped caskets off the plane at Andrews. I put my arms around the mothers and fathers, sisters and brothers, sons and daughters."
Republican questions at the hearings were expected to range from a security vacuum in Northern Africa to new cables suggesting that Stevens once proposed moving the compound to a more secure location adjacent the CIA Annex, sources told CNN.
With several new members on the House Foreign Relations Committee, and two possible GOP presidential hopefuls -- Marco Rubio of Florida and Rand Paul of Kentucky -- on the Senate panel, State Department officials anticipated aggressive questions about whether the presence of Islamic extremists in Mali and Algeria were in any way related to past decisions by the Obama administration to keep U.S. combat troops out of Libya.
However, A GOP member of the committee told CNN that House Foreign Affairs Chairman Ed Royce, R-California, met with Republicans on the committee and urged them to be respectful of Clinton.
Clinton was originally scheduled to testify last month but postponed her appearance as she was treated for illness, a concussion and a blood clot near her brain. The country's top diplomat returned to work just over two weeks ago.
Rep. Jason Chaffetz, R-Utah, said Clinton was "going to get some very hard questions" on the State Department's role in handling security for diplomatic security in Libya before the attack, as well as what Clinton was doing the night of the violence.
"We had an ambassador missing for something like seven hours with no assets brought in" for a response, he told CNN on Wednesday.
An independent report from the Accountability Review Board ordered by the State Department said it did not find "that any individual U.S. government employee engaged in misconduct or willfully ignored his or her responsibilities" leading up to the attack.
However, one State Department official resigned and three others were placed on administrative leave after the report was released in December.
Sources told CNN that congressional staffers have been shown new State Department e-mails and cables indicating that in November 2011, Stevens proposed two options to the State Department for boosting security for diplomats in Benghazi.
The first involved moving the diplomatic compound back into a hotel. The second would have moved the compound to an unoccupied villa adjacent the CIA Annex.
CIA officials agreed with U.S. diplomatic personnel in the country that the latter option would be safer, but the State Department rejected the idea.
It's a position Clinton took soon after the September attack, telling CNN in an interview last October that she was ultimately responsible for security.
There have been more than 30 hearings and closed door briefings on Benghazi with State Department officials present.
Rep. Gerald E. Connolly of Virginia, a Democratic member of the House Foreign Affairs Committee, said Congress has failed to expeditiously fund State Department efforts to upgrade security at high-risk posts. He pointed a finger at House Republican leaders.
"A paucity of resources ingrains a specific culture within any organization, in this case the State Department --- namely that every purchase, every expense, must be justified in a time when the threat of even more cuts loom beyond the horizon," Connolly said in a statement released on the eve of the hearings.
Obama ordered a review of security at all diplomatic outposts in the wake of the attack.
Clinton also was likely to face questions about the storming of the natural gas facility last week in Algeria during which militants seized dozens of hostages. Three Americans lost their lives.
Al Qaeda in the Islamic Maghreb is believed to have had a hand in the attack. Clinton also will likely face questions about the battle against extremists in neighboring Mali.