James Comey, a former Bush administration official who once opposed illegal wire-tapping, has been nominated by US President Barack Obama as the new head of the FBI amid a national debate over the government's secret surveillance programme.
If confirmed by the Senate, the 52-year-old former hedge fund executive would succeed Robert Mueller and serve a 10-year term.
Comey is best known for facing off against the White House officials in 2004 over the legality of the eavesdropping programme of the National Security Agency (NSA).
He was previously the deputy Attorney General under George W Bush. He refused to sign off on a domestic eavesdropping programme where the National Security Agency wiretapped phone calls without warrants.
Obama, whose own administration is now beset by a stream of disclosures over secret government surveillance, referred to the episode as he nominated Comey to lead the FBI.
In nominating Comey, Obama said the former Justice Department official will help strike a balance between the need for information on terrorist plots and respecting Americans' privacy.
Praising his FBI nominee, Obama said Comey is a rarity in Washington who doesn't care about politics.
"Comey understands that in time of crisis, America is judged not only by how many plots or how many criminals are brought to justice, but also by commitment to the Constitution and civil liberties espoused in the Constitution," Obama said.
"As we've seen in recent days, this work of striking a balance between our security but also making sure we are maintaining fidelity to those values that we cherish is a constant mission. I have confidence not only in his experience, but his integrity, that Jim will be a leader who understands how to keep America safe and stay true to our founding ideals no matter what the future may bring," he added.
Mueller, who took over as the FBI director just the week before the September 11 attacks in 2001, will retire after heading the FBI for 12 years.
"Mueller has embodied those values through decades of public service and lived them every day as FBI director during an extraordinary period in our nation's history. He began one of the biggest transformations of the FBI in history to make sure that nothing like that ever happens again," Obama said.
He will need to be confirmed by the US Senate before taking up the post but is not expected to face serious opposition from senators.