WASHINGTON - Sen. Lindsey Graham on Tuesday threatened to block Senate consideration of President Obama's nominee to head the CIA in retaliation for the administration's failure to provide more details about the Sept. 11 attack on the U.S. Consulate in Benghazi, Libya.

The South Carolina Republican's threat to place a hold on the nomination of John Brennan raised doubts about a second national security leadership pick by Obama, with several senators already questioning former Sen. Chuck Hagel's qualifications to be defense secretary.

Criticism over the Benghazi assault from Graham, a Senate Armed Services Committee member who served as a military lawyer in Iraq and Afghanistan, and fellow Republican Sens. John McCain of Arizona and Kelly Ayotte of New Hampshire contributed to U.N. Ambassador Susan Rice's decision last month to withdraw her name for consideration as secretary of state.

Graham brought up Rice again Tuesday in explaining why he is weighing a block of Brennan's nomination to head the CIA. "I have not forgotten about the Benghazi debacle and still have many questions about what transpired before, during and after the attack on our consulate," Graham said.

"In that regard, I do not believe we should confirm anyone as director of the CIA until our questions are answered -- like who changed Ambassador Susan Rice's talking points and who deleted the references to Al-Qaida?" Graham said. "My support for a delay in confirmation is not directed at Mr. Brennan, but is an unfortunate, yet necessary action to get information from this administration."

In appearances on TV talk shows Sept. 16, five days after the Benghazi attack that killed four Americans, Rice described them as spontaneous violent responses to an anti-Islam film produced in the United States.

Her description contradicted subsequent claims by the CIA and other senior U.S. officials, who said the attack was coordinated by Al-Qaida terrorists.

Rice and her defenders later said she had relied in her initial account on talking points provided to her by the White House, but Senate investigators subsequently found that several intelligence agencies had changed them to remove references to Al-Qaida participation in the Benghazi assault.

White House press secretary Jay Carney on Tuesday criticized Graham for threatening to delay Brennan's nomination.

"It would be unfortunate, I think, if in pursuit of this issue, which was highly politicized, the Senate would hold up the nomination of John Brennan.

Carney ridiculed "the continued political fascination with appearances on Sunday [news] shows."