The Democrat-turned-independent lawmaker from Connecticut, who is retiring from the Senate, said the reaction from the U.S. government to the security situation in Benghazi before the attack "was woefully inadequate to the dangers the flashing light was indicating."
The report is largely consistent with the criticism of an independent review panel appointed by Secretary of State Hillary Rodham Clinton. That panel, in a Dec. 18 report, found the State Department had "grossly inadequate" security in Benghazi and must correct "systemic failures" in the protection of diplomats.
Sen. Susan Collins of Maine, the committee's ranking Republican, said the Defense Department couldn't have responded with military forces in time to the initial attack that resulted in the death of Stevens and information specialist Sean Smith.
Yet Collins questioned why U.S. troops could not have responded in time to the second attack at a CIA annex that occurred several hours later. That attack killed two former Navy SEALs, Tyrone Woods and Glen Doherty, who were working as security personnel.
Collins said the Pentagon "has insufficient assets to respond to attacks of this type."
The committee's report calls for the Defense Department to station more troops and other assets "within range on land and sea to protect and defend both Americans and our allies on the African continent."
Clinton, who is in the hospital for a blood clot related to a concussion she suffered, has agreed to testify to Congress on the Benghazi security lapses in January.
Lieberman said there was no evidence of "direct responsibility by Secretary Clinton" for the security lapses. Echoing the finding of the independent review panel, Lieberman said, "It stopped, as far as we can see, at the mid-level managers."
An assistant secretary in charge of diplomatic security resigned from that post and three other officials were placed on administrative leave in the wake of the investigation, the State Department said Dec. 19.
Collins said it's "likely there are others that do need to be held accountable," though she said that decision should rest with Clinton.
The report also faults the Obama administration for giving "inconsistent" descriptions of the attack when it was clear to the intelligence community "from the beginning" that it was a terrorist act.
Initial "talking points" drafted by intelligence officials that were used in the initial days following the attack described the event as a spontaneous protest that spiraled out of control.