US president Barack Obama has named prosecutor Loretta Lynch as his pick to succeed Eric Holder as attorney general.
At a White House ceremony, Mr Obama said Ms Lynch has a fierce commitment to equal justice and a solid record as a tough, fair federal prosecutor.
Lynch, 55, would be the first African-American woman to serve as attorney general. She is currently the top federal prosecutor in Brooklyn, New York.
Outgoing Attorney General Eric Holder also was at Saturday's announcement. Mr Holder was the first black head of the Justice Department.
"Loretta might be the only lawyer in America who battles mobsters and drug lords and terrorists, and still has the reputation for being a charming people person," Obama said to laughter from those who packed the Roosevelt Room for the announcement.
Ms Lynch said she was humbled and thrilled at the prospect of leading "the only Cabinet department named for an ideal."
"If I have the honour of being confirmed by the Senate, I will wake up every morning with the protection of the American people my first thought," she said.
"And I will work every day to safeguard our citizens, our liberties, our rights, and this great nation which has given so much to me and my family."
Republicans have promised tough scrutiny of Mr Obama's pick after years of battles with Mr Holder, who is close to Ms Lynch and appointed her as chair of a committee that advises him on policy.
Mr Holder has been an unflinching champion of civil rights in enforcing the nation's laws and his successor will be left to grapple with several prominent civil rights issues that have been elevated on his watch.
White House officials said they are leaving it up to Senate leaders to work out the timeline for her confirmation, with Mr Obama calling for approval "without delay." But with Democrats facing a long list of priorities before the year's end brings a shift to Republican control, it is likely she will not get a vote until next year.
She was chosen in large part because the White House sees her as likely to win approval among the political divisions in the wake of Republican victories in Tuesday's midterm election.
Ms Lynch is the US attorney for the Eastern District of New York, which covers Brooklyn, Queens, Staten Island and Long Island, a position she also held under President Bill Clinton.
"Loretta doesn't look to make headlines, she looks to make a difference," Mr Obama said. "She's not about splash, she is about substance."