For first time in U.S. history, Republicans filibuster defense secretary nominee

Republicans demanding answers from President Barack Obama's pick to head the Pentagon forced Senate leaders Wednesday to delay a vote, throwing Chuck Hagel's confirmation into doubt.

Senators James Inhofe and Lindsey Graham have expressed strong opposition to rushing Hagel's confirmation process, and after Hagel was narrowly approved by the Senate Armed Services Committee on Tuesday, the Republicans insisted they would try to block a vote in the full Senate.

"This is the first time in the history of our country that a presidential nominee for secretary of defense has been filibustered. What a shame," Senate Majority Leader Harry Reid said on the floor of the chamber.

To overcome the blocking tactic, Reid scheduled a vote on Friday to end debate on the Hagel nomination, but such a procedure requires a 60-vote threshold rather than the typical simple majority.

Democrats hold a 55-45 edge in the Senate. No Democrats are expected to vote against Hagel, a Vietnam War veteran and Republican former senator himself, while just two Republicans have publicly stated their support.