CIA Director nominee John Brennan testifies on Capitol Hill in Washington, Thursday, Feb. 7, 2013, during his confirmation hearing before the Senate Intelligence Committee'. (J. Scott Applewhite/AP)

A Senate confirmation vote on John O. Brennan as CIA director has been postponed for at least two weeks as lawmakers step up pressure on the Obama administration to provide more information about its drone campaign against terrorism suspects.

In particular, Senate Intelligence Committee Chairman Dianne Feinstein (D-Calif.) said Wednesday that she is seeking seven Justice Department memos related to the administration’s targeted killing program, in addition to four the committee has been allowed to view.

Administration officials expressed frustration over the demands and indicated that at least some of the memos the committee seeks do not exist or were superseded by those the lawmakers have already seen.

President Obama pledged in his State of the Union address to make the lethal targeting program “even more transparent to the American people and to the world.” But the administration is wedged between its slow-moving efforts in that direction, after years of secrecy, and congressional insistence on more immediate answers. Brennan’s nomination has provided the Senate Intelligence Committee with leverage to press demands that it has made for the past two years for access to opinions on drone killings written by the Justice Department’s Office of Legal Counsel.

Feinstein had initially indicated that a vote on Brennan would be held this week. But she said that, under committee rules, members “have the ability to object to a vote on the nomination until after Thursday, so the vote will be delayed.”

Her office said members have not had the 48 hours required under their procedures to review a complete transcript of a closed-door hearing they held with Brennan on Tuesday. Congress is in recess next week and will not return until the week of Feb. 25.

In addition, Feinstein said, “members on both sides of the aisle have asked that certain information . . . be provided to the committee” — a sign of deep divisions with the administration over congressional oversight of intelligence matters.

There is little doubt that Brennan will eventually be confirmed. But the delay adds a hurdle to Obama’s effort to get his new national security team in harness. Administration officials, who spoke on the condition of anonymity about intelligence matters, voiced consternation about what they clearly saw as the committee’s effort to hold Brennan, currently Obama’s chief counterterrorism adviser, hostage to the drone issue.

“The thing these guys need to understand on John is that he has been one of the foremost voices in this administration pushing” for the release of more information on targeted killings, one official said.

In an interview last summer and at his public confirmation hearing last week, Brennan said the United States should publicly acknowledge deadly strikes. He has also said he believes that lethal action should be undertaken by the military, rather than the CIA, which has carried out hundreds of drone strikes, most of them in Pakistan but also in Yemen.

Feinstein said the committee had received two Office of Legal Counsel (OLC) opinions related to targeted killings sometime before last week’s hearing. Days before the hearing, an unclassified OLC document was leaked that summarized its justification for the September 2011 drone strike that killed U.S.-born cleric Anwar al-Awlaki in Yemen. The White House subsequently agreed to allow committee members to view that OLC opinion, written in July 2010, as well as an earlier version from February 2010.

In her statement Wednesday, Feinstein referred to seven additional opinions “that we believe to exist on targeted killings.”

Explore documented drone strikes in Pakistan, Yemen and Somalia

Several current and former administration officials questioned her math, which one said was “inflated by a factor of two or three.” They suggested, without providing details, that the documents could have been written under the George W. Bush administration or — like the July 2010 Awlaki opinion — could be expanded versions of earlier documents.

Feinstein and Sen. Saxby Chambliss (Ga.), the committee’s senior Republican, are not the only ones asking for more information. Sen. Ron Wyden (D-Ore.) and others have said that they cannot make a decision on Brennan until the administration responds to their requests for documents specifically related to the targeted killing of U.S. citizens abroad.

Sen. Rand Paul (R-Ky.) further stirred the pot Wednesday, saying he will put a hold on the nomination until Brennan responds to a question posed in the hearing last week about whether he believes “that the president has the power to authorize lethal force, such as a drone strike, against a U.S. citizen on U.S. soil.”

Even if the committee approves Brennan, Sen. Lindsey O. Graham (R-S.C.) has threatened to hold up floor votes on both Brennan and Chuck Hagel, Obama’s defense secretary nominee, unless the White House provides more information about its handling of the Sept. 11, 2012, attack on a U.S. diplomatic outpost in Benghazi, Libya.