UPDATE 1-U.S. Senate confirms Brennan as new CIA director

(Adds detail on Brennan's confirmation)

WASHINGTON, March 7 (Reuters) - The U.S. Senate on Thursday confirmed John Brennan as the Obama administration's next director of the Central Intelligence Agency.

The Senate voted 63-34 in favor of Brennan, overcoming Republican Senator Rand Paul's attempt to slow the White House counter-terrorism advisor from becoming the next head of the CIA.

Paul, who spent nearly 13 hours speaking on the Senate floor on Wednesday, was irate about the reluctance of President Barack Obama's administration to declare that "targeted killings" of American citizens on U.S. soil were unconstitutional.

Attorney General Eric Holder then clarified the administration's policy on Thursday and said that Obama would not use his authority to order a drone to kill an American on U.S. soil who was "not engaged in combat."

Holder initially declined to declare the targeted killings would be unconstitutional, saying that there could be situations, similar to the Sept. 11 al Qaeda attacks on New York and Washington in 2001, in which such killings might be appropriate.

Ted Cruz, another Republican senator who tried to slow Brennan's confirmation, said that under questioning, Holder would only declare that such killings were inappropriate, but he eventually acknowledged they would be unconstitutional.

Paul's 13-hour speech was the latest twist in a convoluted confirmation process that delayed Brennan's Senate confirmation for weeks.

The nomination became a vehicle for Republicans and some Democratic critics to pressure the White House to disclose sensitive government records. These included emails and documents related to targeted killings and the administration's response to the attack last year on a U.S. diplomatic compound in Benghazi, Libya. (Reporting by Rachelle Younglai and Mark Hosenball; Editing by Christopher Wilson)