Clinton testifies on Benghazi attacks to Congress (LIVE VIDEO)

US Secretary of State Hillary Clinton testified to Congress on Wednesday about the deadly September attack on a US diplomatic facility in Benghazi, Libya.

"I take responsibility," Clinton said early in her remarks. She added soon after, "Taking responsibility meant moving quickly" when the attacks first took place.

Clinton didn't shy away from acknowledging systemic failures that impaired the State Department's response in Benghazi. But she also emphasized the uphill battle of countering terrorism.

“Our security professionals get it right more than 99 percent of the time” against difficult odds, she said.

"If you wish to fault the administration, it's that we didn't have a clear picture and didn't do a good enough job of explaining we didn't have a clear picture," she said near the end of the meeting.

Clinton described watching the caskets of those killed in Benghazi being carried off a plane at Andrews Air Force base. Talking about consoling the families of the dead, Clinton's voice became hoarse as she fought back tears.

"Nobody knew the dangers better than Chris," she said later, explaining her decision to appoint Ambassador Chris Stevens to a post in Libya, where he later lost his life.

"The two hardest calls I made were to the families of Ambassador Stevens and Sean Smith," she said, while describing her day on September 11 last year.

"These new countries have no experience with democracy," Clinton said, referring to north Africa and the Arab Spring countries. "We have to recognize this is a global movement," she continued, saying that the US should be invested in fostering democracy in those countries.

The recent attack in Algeria came up as a topic, while Clinton stressed, "We cannot permit Mali to become a safe haven." The Islamist militants involved in Algeria claimed that their kidnapping of dozens of foreign workers at a gas complex were in retaliation for France's intervention in Mali.

She pointed out that some of the Islamist rebels active in Algeria and Mali had been employed by the late dictator Muammar Gaddafi in Libya before his demise. Their connection to Gaddafi also allowed them access to numerous weapons, she said.

"This Pandora's box of weapons coming out of the Middle East and North Africa is one of our biggest problems," Clinton said.

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When asked about the confusion over UN Ambassador Susan Rice's talking points, when Rice said the attack on Benghazi was part of protests and not a terror attack, Clinton said, "I was not focused on talking points. I was focused on keeping our people safe."

Later, in response to another question from senate Republican Ron Johnson on Rice's talking points, Clinton showed some temper, thumping the table and saying in a raised voice, "With all due respect, the fact is we had four dead Americans."

"Was it because of a protest or because of guys out for a walk one night who decided to go kill some Americans? What difference at this point does it make? It is our job to make sure that it doesn't happen again."

Sen. John McCain greeted Clinton, saying it was nice to see her well and "combative as ever." McCain, like a majority of Republican senators before him, questioned the discrepancy of attributing the Benghazi attack to protests gone awry or to a pre-planned attack.

"People don't bring RPGs and mortars to spontaneous demonstrations. That's a fundamental," McCain said.

"Core Al Qaeda certainly has been [decimated]," Clinton insisted. What we're seeing now, she said, is people who have migrated back to their home countries, and formed affiliates. "We do have to contend with the wannabes and the affiliates going forward."

Sen. Rand Paul, a Republican from Kentucky, said Clinton leaving her post should be viewed as her accepting culpability for the Benghazi attack, calling it the worst tragedy since 9/11. "I don't suspect your motives of wanting to serve your country, but I think it was a failure of leadership."

Clinton said, "Let's be honest with ourselves. Let's avoid trying to turn everything into political football."

"Let's bring people together to have an open discussion that really used to be the hallmark of this committee and of the Senate."

New Jersey Senator Bob Menendez delivered opening remarks, in which he called Clinton's service at State "exemplary."

"You have changed the face of America abroad," he said.

But the glowing reviews, from a fellow Democrat, may fade as the hearing proceeds. BBC News reported that though Clinton would be treated with respect in the Senate, where Democrats hold the majority, in the House, she is expected to face much more pressure. NBC News wrote that for Clinton, the political stakes are incredibly high.

According to Voice of America, Clinton is expected to face questions about security failures associated with the attack, which killed four US citizens, including Ambassador Chris Stevens.

An independent report into the attacks found "profoundly weak" security at the US mission in Benghazi, and that there was a pervasive sense among the people working at the compound that their security wasn't a priority for the State Department.

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Sen. Marco Rubio of Florida, already pegged to be a major contender for the 2016 elections, will most likely make his mark while interrogating Clinton, NBC News predicted. The stand-off could be a determination for the 2016 race, as Clinton herself is considered a strong contender for the Democratic nomination.

Clinton has previously taken responsibility for what went wrong in Benghazi. Though a panel review didn't find Clinton directly responsibility for the attack, members of Congress will want to know why she was not more aware of the requests for further security by the mission.

Clinton is stepping down from her post in two weeks, and has spent the last month recuperating from a series of illnesses in December.