John Brennan took over as director of the CIA today, the finishing touch on president Barack Obama's national security team for his second term.
The White House said vice president Joe Biden swore Mr Brennan in during a private ceremony in the Roosevelt Room, the morning after he won Senate confirmation amid a contentious debate. Republicans had blocked his nomination but lifted their delay after the administration bowed to their requests for clarification about the president's power in using drones.
Last week Chuck Hagel won Senate confirmation to be defence secretary, joining secretary of state John Kerry in Mr Obama's revamped second-term line-up.
The Brennan vote was 63-34 and came hours after Republican Senator Rand Paul, a possible 2016 presidential candidate, used an old-style delaying tactic called a filibuster of the nomination to extract an answer from the administration on the drone question.
Mr Brennan, a 25-year CIA veteran, won some Republican support. Thirteen Republicans voted with 49 Democrats and one independent to give Mr Brennan, who has been Mr Obama's top counter-terrorism adviser, the top job at the nation's spy agency.
He replaces Michael Morell, the CIA deputy director who has been acting director since David Petraeus resigned in November after acknowledging an affair with his biographer.
The confirmation vote came moments after Democrats prevailed in a vote ending the filibuster, 81-16.
In a series of fast-moving events, by Senate standards, attorney general Eric Holder sent a one-paragraph letter to Mr Paul, who held the floor for nearly 13 hours on Wednesday and into Thursday.
"It has come to my attention that you have now asked an additional question: 'Does the president have the authority to use a weaponised drone to kill an American not engaged in combat on American soil?'," Holder wrote. "The answer to that question is no."
That cleared the way.
"We worked very hard on a constitutional question to get an answer from the president," Mr Paul said after voting against Mr Brennan. "It may have been a little harder than we wish it had been, but in the end I think it was a good healthy debate for the country to finally get an answer that the Fifth Amendment applies to all Americans."
The amendment in the US Constitution protects citizens against abuse of government authority.
However, Mr Paul's filibuster of the Brennan nomination troubled the Republican party with majority leader Mitch McConnell, libertarians and conservative tea party members rallying to the freshman senator's side and military hawks such as John McCain and Lindsey Graham arguing that Mr Paul's claims were unfounded.