US National Security Advisor Thomas Donilon has resigned his post, with US Ambassador to the United Nations, Susan Rice, getting ready to take his place in July.
White House officials confirmed the change on Wednesday, adding that the 58-year-olds resignation will take effect early next month.
The announcement came ahead of a planned broadcast by US President Barack Obama later in the day.
The US president is expected to name Rice as his national security adviser, an appointment which does not require a confirmation in the Senate.
Obamas move is seen as a rebellious gesture against Republicans who pushed the president into withdrawing her nomination for secretary of state earlier in the year.
Rice came under intense fire from Republicans for characterizing the September 11, 2012, attack on the US Consulate in the eastern Libyan city of Benghazi as a spur-of-the-moment response to a blasphemous US-made movie that insults Islam and Prophet Muhammad (PBUH).
Obama is also expected to name Samantha Power, a former White House adviser, as the next US ambassador to the United Nations.