The Republican chairman of the House oversight panel is asking a veteran diplomat and a former chairman of the Joints Chief of Staff for sworn testimony about their investigation into the deaths of four Americans at a diplomatic outpost in Benghazi, Libya.Today Rep. Darrell Issa plans to pursue depositions from retired Ambassador Thomas Pickering and retired Adm. Mike Mullen.

Issa wants to know with whom the pair spoke to reach their conclusion that then-Secretary of State Hillary Rodham Clinton did not direct the response to the pair of nighttime attacks in Libya.

Pickering says there is no evidence high-level State Department officials were responsible.

Issa spoke with NBC's "Meet the Press." Pickering spoke with CNN's "State of the Union," CBS' "Face the Nation" and NBC.

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