(CNN) - Samantha Power, special assistant to the president and senior director for multilateral affairs and human rights at the National Security Council, will be stepping down later this month, a White House official said Thursday.
She's considered the leading candidate to become U.S. ambassador to the United Nations should Ambassador Susan Rice leave her post.
"After four years at the White House, Samantha will be leaving the NSC later this month and will spend some well-deserved time with Cass and her two small children, Declan (3) and Rian (eight months)," the official said in a statement.
While she is "likely" to return to the administration, the official added "no decisions have been made on her next steps."
"Samantha has been a powerful voice in this administration and a long-time friend and adviser to the President. We will miss her at the NSC, and we look forward to continuing the President's work promoting human rights and dignity," the official said.
The Obama administration is also experiencing other changes. Democratic sources say Jeff Zients, the acting director of the White House Office of Management and Budget, is the leading candidate to become the next U.S. Trade Representative.
As for the Environmental Protection Agency, the assistant administrator for the office of air and radiation, Gina McCarthy, is the top candidate for the agency.
However, former Washington Gov. Christine Gregoire has been discussed as a possibility for the role.
Bob Perciasepe, EPA deputy administrator, was interviewed for the job but is unlikely to get it, sources say, given the Obama administration's desire for more diversity in the cabinet.