Secretary of State Hillary Rodham Clinton is challenging Republicans for focusing on the comments made by U.N. Ambassador Susan Rice in the days after the attack on the U.S. consulate in Libya that killed four Americans in September.

U.S. Secretary of State Hillary Clinton testifies before the Senate Foreign Relations Committee (Alex Wong/Getty Images)

Rice initially said the attack resulted from protests, rather than terrorism.

Testifying to a Senate panel today, Clinton asked, "What difference, at this point, does it make?" She says she's focused on improving security, rather than on revisiting the "talking points" used by Rice.

Clinton said her department is moving swiftly and aggressively to strengthen security at U.S. missions worldwide. She again took responsibility for the department's missteps leading up to the assault at the consulate in Benghazi.

Republican Sen. John McCain dismissed Clinton's explanation of events, and also criticized the administration's response to warnings about a worsening security situation in Libya.

Slain diplomat's family: Clinton has sent regrets

Ambassador Chris Stevens' stepfather says Secretary of State Hillary Clinton has reached out to his family to offer her sympathies about the deadly Sept. 11 raid on the consulate in Libya that killed his stepson.

Still, the family is avoiding discussions of whether security was adequate as Clinton testified Wednesday on Capitol Hill about the department's missteps leading up to the assault at the U.S. facility in Benghazi.

Bob Commanday, of Oakland, says Clinton met with the family and has written them several times to express her regrets.

Commanday says the family has received no privileged information about the adequacy of diplomatic security leading up to the assault.

Clinton: 'very promising leads' on Benghazi attack

U.S. Secretary of State Hillary Clinton (Chip Somodevilla/Getty Images)

Clinton says the FBI is "following some very promising leads and putting together cases" as they investigate the Sept. 11 attack on the diplomatic mission in Benghazi that killed the U.S. ambassador to Libya and three other Americans.

Clinton told lawmakers on Wednesday that she had gotten an update on the probe in recent days from FBI Director Robert Mueller, who returned from a trip to Libya last week. She said the FBI is now trying to determine "how best to respond" to the leads they have.

But Clinton vowed that those responsible for the attack would be brought to justice even if it takes some time.

"We will respond," she said.

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