Samantha Power testifies before a Senate Foreign Relations Committee confirmation hearing on her nomination to succeed Susan Rice as U.S. ambassador to the U.N. (Reuters)

As the United States' newly sworn-in ambassador to the United Nations, Samantha Power emphasized the power of individuals and the inefficiency of bureaucracy in her first public address.

Speaking to youth activists attending the Fourth Estate Leadership Summit at UCLA, Power detailed her early career as a foreign correspondent and her discovery of what she called "the role of the citizen." To close the weekend conference, Power praised the sacrifices of young activists and criticized years of bureaucracy at organizations such as the United Nations.

“Bureaucracies are built. Positions become entrenched," she said. "And while the United Nations has done tremendous good in the world, there are times when the organization has lost its way, when politics and ideology get in the way of impact."

About 2,000 high school and college students attended the four-day conference, which was hosted by Invisible Children, an advocacy group that seeks to end the violence of the Lord's Resistance Army, a Ugandan guerrilla movement known for abducting children to use as soldiers.

Power, a longtime foreign policy adviser to President Obama, commended Invisible Children's recent effort, a 2012 video campaign that she said resulted in the creation of a rewards program to encourage the arrest of LRA leader Joseph Kony. "Because of you," Power told the cheering audience, Secretary of State John F. Kerry will now offer the first cash reward to bring Kony to justice.

"What matters are results," she said. "Everything else is just noise."

Power, 42, is the youngest person to hold her office. Following her Senate confirmation on a vote of 87 to 10, she succeeded Susan E. Rice, now Obama's national security adviser.