An up-or-down vote on confirmation, with only a majority necessary, could occur as early as Wednesday.
The filibuster left the administration angry and troubled by the prospect of a nomination in limbo, with opposition groups redoubling their efforts to scuttle Hagel and the uncertainty of a weeklong Senate break. But the administration is more confident about Hagel's prospects after private conversations with several senators to ensure Hagel gets past the 60-vote barrier, according to an official close to the confirmation process. The official spoke on condition of anonymity because he was not authorized to discuss private conversations.
Hagel's nomination also has become entangled in GOP demands for more information from the Obama administration about the deadly assault on the U.S. diplomatic mission in Benghazi, Libya, last September that killed Ambassador Chris Stevens and three other Americans.
Sen. Lindsey Graham, R-S.C., has described Hagel as "radical" and pressed for Obama to abandon the nomination. Graham sent a new letter to Hagel this week with fresh questions about Israel, after Hagel responded to a separate Graham letter on Israel last week.
Associated Press writer Darlene Superville contributed to this report.
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