The White House has agreed to turn over to the Senate Intelligence Committee additional emails and intelligence reports related to the lethal attack on the U.S. mission in Benghazi, Libya, according to a congressional source.

The source said some of the materials have already been received by the panel and others "will be provided shortly."

Republican senators have threatened to hold up the nomination of John Brennan as CIA director until they receive e-mails exchanged between the White House and the spy agency concerning public talking points about the deadly attack last September 11.

U.N. Ambassador Susan Rice relied on those talking points to explain the Obama administration's version of events several days after the armed assault. Her televised comments ignited an election-year controversy, fueled by Republicans, over whether the administration was being truthful about the nature of the attack.

Rice said it apparently grew from a demonstration over an anti-Muslim film, but it was later disclosed that it was a terror assault.

U.S. Ambassador to Libya Christopher Stevens was one of four Americans killed.

The CIA's original draft of talking points linked individuals associated with al Qaeda to the attack. But the final version changed the al Qaeda reference to extremists.

Some Republicans have accused the administration of deliberately downplaying the attack to protect the Obama administration in the middle of a presidential election.

The lawmakers have been unsatisfied with what they say is conflicting information from the administration about who was responsible for the change in the talking points although the CIA eventually said it changed them during discussions among various agencies to protect classified information and for legal reasons.

National Security Council spokesman Tommy Vietor said the White House has been talking to the intelligence committee about its Benghazi requests and will continue to do so, but there is nothing to announce at this point.

Vietor noted the executive branch has already provided "10,000 pages of documents, 6 witness hearings, 5 hours of testimony by (Defense Secretary Leon) Panetta, 5 more by(then Secretary of State Hillary) Clinton, (and) answered 40 Benghazi related inquiries."

Sen. Lindsay Graham, R-South Carolina, who is not a member of the intelligence committee, has also criticized the administration's immediate response to the attack. He has demanded more information about action taken by President Barack Obama to help those under siege.

Separately, Democrats on the intelligence panel have also requested the administration turn over additional Justice Department opinions on the use of targeted killings of Americans overseas.

The White House provided two legal opinions from the Office of Legal Counsel a couple of weeks ago, but Sen. Dianne Feinstein, chairman of the committee, said there are seven additional OLC opinions the panel should review. But so far, the administration has refused to turn them over.

Feinstein plans to schedule a committee vote on the Brennan nomination when Congress returns next week from its recess and it appears Brennan has enough support.

How quickly the full Senate will move ahead with a final vote depends on whether lawmakers are satisfied with the administration's response to their requests.

Moreover, there is another wrinkle for Brennan.

Senator Rand Paul (R-Kentucky) has also threatened to hold up his nomination until he gets answers to his question about whether the administration would use targeted killings against Americans at home.

In a written response to the committee last week, Brennan said the administration has "no intention" of killing Americans with drone strikes in the United States.

But Paul said he was not satisfied, writing in a letter to Brennan on Thursday that he will do everything he can to block the nomination until he gets a proper answer.