A White House official says Tom Donilon is resigning as President Obama's national security adviser and will be replaced by Susan Rice.
Rice is currently the U.S. ambassador to the United Nations. She has been harshly criticized by Republicans for her initial accounting of the attacks on a U.S. compound in Benghazi, Libya, which later proved to be incorrect.
Donilon's resignation marks a significant shakeup for Obama's national security team.
The official insisted on anonymity in order to discuss the personnel changes before they were publicly announced.