(USA TODAY) -- President Obama will appoint United Nations ambassador Susan Rice as his new national security adviser, replacing Tom Donilon, officials said Wednesday.

Obama also plans to nominate former National Security Council aide Samantha Power to replace Rice as U.S. ambassador to the United Nations.

Obama had considered Rice for Secretary of State late last year, but appointed John Kerry instead in part because of controversy surrounding the Sept. 11 attack in Benghazi, Libya.

White House officials confirmed the appointment on the condition she not be named, so as not to pre-empt Obama's formal announcement later on Wednesday.

Rice is a longtime associate of the president, working as foreign policy adviser during his 2008 campaign.

Senate Republicans had threatened to block Rice's nomination to the State Department, but the national security adviser's job does not require Senate confirmation.

The job switch comes as Obama prepares for a summit with Chinese President Xi Jinping; Donilon was in Beijing recently preparing for the meeting.

Officials said Donilon is expected to stay on the job until July, working with Obama on planned trips to Europe and Africa.

Donilon's retirement has been expected sometime this year, and Rice has long been considered the top candidate for his replacement.

Among Rice's new challenges: The U.S. reaction to the civil war in Syria and violence throughout the Middle East, sometimes testy relationships with China and Russia, and completing the end of U.S. combat operations in Afghanistan.

Republicans investigating Benghazi have criticized Rice over television interviews she gave five days after the attack, attributing it to protests over an anti-Islam film. After the administration later called it a pre-planned terrorist attack, GOP members accused Rice and others of an attempted cover-up.

Rice said she discussed the attack based on the evidence known at the time, while Obama and aides accused the Republicans of a partisanship.

In a Nov. 14 news conference, Obama said that Rice has done "exemplary work" at the U.N.

"She has represented the United States and our interests in the United Nations with skill and professionalism and toughness and grace," Obama said.

The job of ambassador to the United Nations does require Senate confirmation.

In nominating Power for that post, Obama picked a former campaign aide, Harvard professor and author who has specialized in genocide and human rights. She won a Pulitzer Prize for her 2002 book, A Problem From Hell: America and the Age of Genocide.

In addition to her work on the National Security Council, Power chaired the Atrocities Prevention Board that Obama created in 2012.

Power had to leave the presidential campaign in the spring of 2008 after describing then-rival Hillary Rodham Clinton as a "monster" who would stop at nothing to defeat Obama. Power apologized for the remark.

After the election, Obama put Power on the NSC and made Clinton his first secretary of state.

Donilon has worked for Obama throughout his presidency, first serving as deputy national security adviser. Obama appointed him to the top job in October of 2010, following the departure of James Jones.

Officials said Donilon helped improve U.S. relations with Asia, wind down the wars in Iraq and Afghanistan, and coordinate the raid that killed 9/11 architect Osama bin Laden in 2011.

Donilon was also the subject of a recent profile in Foreign Policy magazine that said he "allegedly undercuts or elbows aside challenges to his power."

White House Chief of State Denis McDonough -- also a former Donilon deputy -- told Foreign Policy that "Tom is a key adviser to the president. He has teed up over the course of these years many important decisions for the president and the country. I really appreciate the work that he does,"

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