A leading Republican senator is threatening to hold up Senate confirmation of President Barack Obama's nominees to lead the Pentagon and the CIA until the White House provides more answers about the Sept. 11 attack against a U.S. diplomatic facility in Benghazi, Libya.

South Carolina Sen. Lindsey Graham is angered by what he calls White House "stonewalling" about the attack that killed four Americans.

Graham tells CBS' "Face the Nation" that he'll hold up Senate action on the nominations of Chuck Hagel to be defense secretary and John Brennan to be CIA director until he gets what he wants from the White House.

The senator wants to know what Obama was doing during the time of the attack and whether he was in touch with Libyan officials.

Democratic Sen. Jack Reed of Rhode Island calls Graham's threat "unprecedented and unwarranted" and says senators should have the chance to vote on the nominees.