Congressional Republicans focused on security lapses exposed by the assault and on whether the Obama administration deliberately played down the terrorist origins of the attack.
Secretary of State Hillary Rodham Clinton is asking Congress for an additional $750 million to hire about 150 more security officers, a deputy said. She had been scheduled to testify Thursday but canceled because of an illness. She said she would testify in January.
The Pentagon has agreed to send about 225 more Marine guards to medium- and high-threat diplomatic posts, Deputy Secretary of State Thomas Nides told the Senate Foreign Relations Committee.
Clinton's other senior aide, Deputy Secretary William Burns, told a House committee later that the department will be "relentless" in trying to follow through on investigators' recommendations to keep diplomats safer.
"We clearly fell down on the job with regard to Benghazi," he said.
House Foreign Affairs Committee Chairman Rep. Ileana Ros-Lehtinen (R., Fla.) suggested that the State Department might do better to examine its priorities before asking for more money.
"We cannot expect the same bureaucracy at State, whose management failures are now manifest, to objectively review the department's organization, procedure and performance," she said. "Nor can we have any confidence in their assessment of what went wrong and what actions are needed to prevent a repeat."
The Accountability Review Board report on the attack released Tuesday found that "grossly" inadequate security and reliance on local militias left U.S. personnel vulnerable.
Senate Foreign Relations Committee Chairman John Kerry (D., Mass.) said some in the State Department did not "see the forest for the trees" as security conditions worsened in Benghazi.