By Matt Spetalnick and Alister Bull
WASHINGTON (Reuters) - Newly retired General David Petraeus was sworn in as CIA director on Tuesday, taking over at a time when the line between the U.S. spy agency and the military has become increasingly blurred in the fight against Islamist militancy.
Petraeus, who in a storied 37-year Army career rose to become arguably the military's brightest star as he worked in Iraq and Afghanistan, took the oath of office from Vice President Joe Biden and then went straight into his first intelligence briefing with President Barack Obama.
"There is literally no time to waste. The president wants him on the job," Biden said at a brief White House ceremony.
Petraeus later addressed a meeting of the spy agency's worldwide staff from an auditorium at the CIA's Langley, Virginia, headquarters.
In his speech to CIA employees, Petraeus highlighted the importance of cutting-edge technology, agile operations and independent analysis, the CIA said.
Petraeus' endorsement of independent analysis was notable. There has been concern among some intelligence veterans that Petraeus might find it difficult to move from being a commander who advocated particular military strategy to that of an intelligence chief who provided objective analysis of policy results and prospects.
The agency said Petraeus, 58, also answered questions from staff about his leadership style, his goals for the CIA and the agency's relationship with more than a dozen other agencies that constitute the U.S. intelligence "community."
Obama enlisted Petraeus to take over at the CIA as part of a major shuffle of his national security team, which included Leon Panetta moving from CIA chief to defense secretary.
Petraeus was credited with helping to turn around the Iraq war and also set in motion Obama's revamped strategy in Afghanistan aimed at halting the momentum of Taliban insurgents and laying the groundwork for a gradual troop withdrawal.
Petraeus takes over at the CIA less than a week before the 10th anniversary of the September 11 attacks on New York and Washington that drew the United States into a protracted fight against al Qaeda and its Islamist allies.
Petraeus thanked Obama for an "extraordinary" opportunity while Biden heaped praise on Petraeus, who was in a business suit for his first day as head of the civilian spy agency.
"You have led and trained the 9/11 generation to become the greatest group of warriors this country has ever seen," Biden said.
Questions remain about how Petraeus will battle the perception of further "militarization" of the CIA.
His decision to retire from the Army, where he rose to the rank of four-star general, is meant to ease the transition.
As CIA chief, Petraeus is expected to embrace the agency's covert drone strikes in Pakistan, which have fueled anti-American sentiment there but have struck at senior militants, including al Qaeda's No. 2 killed on August 22.
Petraeus's new role puts him in charge of handling delicate relations with Pakistani secret services, severely strained after they were surprised by the U.S. raid that killed Osama bin Laden in May.
Petraeus has dismissed concerns he would be unable to provide objective intelligence advice on the wars in Afghanistan and Iraq -- where the level of violence also remains high -- after leading those campaigns.
Known for mixing military know-how with political savvy, Petraeus originally was distrusted by the White House until he lowered his public profile as a top war commander.
His acceptance of the CIA post put an end to Washington speculation that he might be drafted by Republicans as a presidential or vice presidential candidate to challenge Obama and Biden in the 2012 election.
Petraeus, who has gained respect across party lines, easily won Senate confirmation in June.
(Additional reporting by Phil Stewart and Mark Hosenball; Editing by Mohammad Zargham, Eric Beech and Bill Trott)