The highly critical report says the US military was not positioned to help the Americans in need, though the head of Africa Command had offered military security teams that Stevens who was killed had rejected weeks before the attack.
Republicans have criticized the Obama administration over the Benghazi assault, in part because then-UN Ambassador Susan Rice initially blamed the violence on mob protests over an anti-Islamic film.
Militants overran the temporary US mission on September 11, 2012, and later that night, when militants fired mortars at the nearby CIA annex where the Americans had taken shelter.
Republicans have said the Obama administration has been covering up what they consider misdeeds before, during and after the attack.
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Committee chairman Dianne Feinstein, says she hopes the report will put to rest conspiracy theories about the militant attacks that night. Vice chairman Saxby Chambliss says the report shows despite a deteriorating security situation in Benghazi, the US government did not do enough to prevent the attacks or to protect the diplomatic facility.
The report also says the State Department should not rely on local security alone in countries where the host government cannot provide adequate protection.
The report notes that the State Department in 2012 continued to operate the Benghazi facility, despite US intelligence reports showing the danger was growing.
The report faults the military for being unable to help when needed. "No US military resources in position to intervene in short order in Benghazi to help defend" the US facilities in Benghazi, it says.