In a joint appearance in Washington Wednesday with Kazakhstan Foreign Minister Yerlan Idrisov, Clinton said a thorough and transparent investigation is being conducted into the attack, in which U.S. Ambassador to Libya Christopher Stevens and three other Americans were killed, CBS News reported.
"There are continuing questions about what exactly happened in Benghazi on that night three weeks ago," she said. "And we will not rest until we answer those questions and until we track down the terrorists who killed our people."
Clinton said "nobody will hold [the State Department] more accountable than we hold ourselves, because we served with and we knew the four men that we lost. They are not just names or profiles to us. They are our colleagues and our friends."
The Obama administration is targeting militants in Libya for a possible reprisal for the attack in Benghazi, officials told The New York Times.
The Defense Department's top-secret Joint Special Operations Command, working with the CIA and Libyan authorities, is preparing "target packages" of suspected militants ahead of possible orders from President Barack Obama, senior military and counter-terrorism officials told the newspaper.
The orders would be to kill or capture assailants determined to have participated or been complicit in the attack, they said.
The 5-hour attack Sept. 11 on the unmarked mission and nearby annex with rocket-propelled grenades, hand grenades, AK-47 and FN F2000 NATO assault rifles, gun trucks and mortars also killed Foreign Service Information Management Officer Sean Smith and private security employees and former U.S. Navy SEALs Glen Doherty and Tyrone Woods.
Two other Americans were injured in the attack, which U.S. Ambassador to the United Nations Susan Rice asserted Sept. 16 was a "spontaneous" protest that turned violent in reaction to a video produced in the United States and widely disseminated throughout the Arab and Muslim world that mocked the Prophet Muhammad.
The administration's description of the attack later changed, with White House press secretary Jay Carney saying Sept. 20 it was "self-evident" the assault was "a terrorist attack" and Clinton linking it to al-Qaida in the Islamic Maghreb, an al-Qaida affiliate originating in Algeria.
The Pentagon and CIA are targeting perhaps a dozen members of al-Qaida in the Islamic Maghreb and Ansar al-Shariah, an Islamist militant group known to operate in Benghazi, the Times said.
Shortly after the Benghazi attack, U.S. spy agencies intercepted electronic communications of Ansar al-Shariah fighters bragging about their exploits to an al-Qaida in the Islamic Maghreb operative, the Times said.
Obama's retaliation options include drone strikes, Special Operations raids like the one that killed al-Qaida founder Osama bin Laden, and joint missions with Libyan authorities, the Times said.
No decisions have been made on any potential targets, administration officials told the newspaper.
The Defense Department and CIA declined to comment.
U.S. counter-terrorism officials now say Ansar al-Shariah probably had a general attack plan for the Benghazi mission "on the shelf" and then set it in motion after word got out demonstrators had breached the walls of the U.S. Embassy in Cairo earlier Sept. 11, a U.S. official told the newspaper.
While the Obama administration has sent extra Marines to protect U.S. diplomatic outposts across the region, it has not yet responded militarily to the Benghazi killings.
The report comes as House Republicans accused the State Department of turning down "repeated" security-increase requests from U.S. diplomats in Libya who said they believed the mission was a vulnerable target.
"Multiple U.S. federal government officials have confirmed to the committee that, prior to the Sept. 11 attack, the U.S. mission in Libya made repeated requests for increased security in Benghazi," House Oversight and Government Reform Committee Chairman Darrell Issa, R-Calif., and National Security, Homeland Defense and Foreign Operations subcommittee Chairman Jason Chaffetz, R-Utah, said in a letter to Clinton Tuesday.
"The mission in Libya, however, was denied these resources by officials in Washington," the letter said.
Clinton wrote back pledging the State Department's full cooperation in getting to the bottom of the Benghazi attack.
The letter to Clinton said whistle-blowers told the Oversight Committee the Benghazi consulate was threatened and attacked 13 times before the deadly assault.
A June 6 attack blew a hole at the consulate's perimeter gate that was "big enough for 40 men to go through," the letter said.
The Daily Beast reported Sept. 26 U.S. intelligence agencies knew within 24 hours of the attack it was planned and was the work of al-Qaida affiliates.
Libyan President Mohamed Magariaf told NBC News Sept. 26 the attack was pre-planned and the anti-Islam film had "nothing to do with" it.
Issa scheduled a committee hearing Oct. 10 to review the allegations and investigate possible security failures in Libya.