A former top diplomat in Libya has been telling members of Congress today about a 2 a.m. phone call from then-Secretary of State Hillary Rodham Clinton in the middle of the deadly assault on the U.S. diplomatic mission in Benghazi, Libya.

State Department foreign service officer and former deputy chief of mission/charge d'affairs in Libya, Gregory Hicks testifies before the House Oversight and Government Reform Committee during a hearing titled, "Benghazi: Exposing Failure and Recognizing Courage" in the Rayburn House Office Building on Capitol Hill (Chip Somodevilla/Getty Images)

The call came amid confusion about the fate of U.S. Ambassador Chris Stevens and fears about the safety of additional American personnel.

Gregory Hicks says Clinton asked him what was going on, and that he briefed her on developments -- mostly dealing with the search for Stevens. He says he told Clinton that Americans in Benghazi would have to be evacuated -- and that she said that was the right thing to do.

Hicks recounted what he called the saddest phone call of his life -- getting word from a Libyan official that Stevens had been killed. Three other Americans also died.

Today's hearing is the latest development in a long-running dispute between the administration and congressional Republicans who have challenged the White House actions before and after the deadly assault.

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