Biden said USAID will coordinate America's work to lead a global response to combat the coronavirus and help the most vulnerable nations.
He called Power, 50, who was born in Britain to Irish parents, raised in Ireland, and became a U.S. citizen in 1993, "a world-renowned voice of conscience and moral clarity."
Power, a graduate of Yale University and Harvard Law School, worked as a journalist during the Balkan wars in the early 1990s and served as U.N. ambassador from 2013 to 2017. She won a Pulitzer Prize in 2003 for her book "A Problem from Hell: America and the Age of Genocide," about the U.S. foreign policy response to genocide.
"As a journalist, activist, and diplomat, I've seen the world-changing impact of USAID," she said in a tweet. "At this critical moment, I feel immensely fortunate to have the chance to serve again, working with the incredible USAID team to confront COVID-19, climate change, humanitarian crises, & more."
Power,. a forceful for advocate for multilateral diplomacy that Trump has shunned, is married to constitutional scholar Cass Sunstein. She had been critical of Hillary Clinton in the 2008 Democratic primaries and famously called her a "monster" in an interview with a Scottish newspaper.
As such, she was a controversial choice for Obama to appoint to the NSC in 2009 yet overcame differences with Clinton's team and replaced Susan Rice as U.S. envoy to the U.N. when Obama named Rice his national security adviser after winning reelection in 2012.
This story has been corrected to show the year Power joined the NSC was 2009, not 2017.