US President Barack Obama
US President Barack ObamaReuters

President Barack Obama is set to name former aide Samantha Power as the U.S. ambassador to the United Nations, a White House official said Wednesday afternoon

Power will replace Susan Rice, who will take over as Obama's national security adviser, The Huffington Post reported.

Power, a longtime adviser for President Obama, left the administration in February but was considered the favorite to replace Rice at the U.N.

She worked on his 2008 presidential campaign and was senior director for multilateral affairs and human rights during the president’s first term in office.

The White House official insisted on anonymity in order to confirm the appointment before it was publicly announced later Wednesday afternoon.