WASHINGTON - US Education Secretary Arne Duncan, one of the few original members of President Barack Obama's Cabinet who are still in office, will step down in December.
Obama has selected Deputy Secretary of Education John B. King Jr to replace him, according to a CNN report, and is expected to speak on the matter at 3.30pm ET (3.30am Saturday Singapore time).
In an internal memo to Department of Education staff, Duncan cited the commute between his home and family in Chicago in announcing his departure and called his job as the "greatest honour of my life".
"We have been lucky to have an a amazing team here from Day One, but I honestly believe our team today is the strongest it's ever been," Duncan wrote.
"So it's with real sadness that (I) have come to recognise that being apart from my family has become too much of a strain, and it is time for me to step aside and give a new leader a chance."
Obama brought Duncan with him to Washington from Chicago, where he served as the city's schools chief.
He has long been one of the President's closest friends in the administration, said CNN - their relationship forged in the days before either came to national prominence.
Duncan, along with Obama's first chief of staff Rahm Emanuel and senior advisers Valerie Jarrett and David Axelrod, formed a home-town crowd for the Obamas when they arrived to the White House.
Jarrett remains in her post at the White House, though Axelrod and Emanuel have both returned to Chicago - Emanuel as the city's mayor, and Axelrod as chair of a politics institute at the University of Chicago.
Duncan said he had not made a decision about his next steps besides spending time with his family, and added that he expected to find work that involved "expanding opportunity for children".
He also offered effusive praise for his deputy and his successor.
"Over the years that I have known him, and especially in the months we have worked together here, I've come to recognise John as one of the most passionate, courageous, clear-headed leaders in our field," Duncan said.
Duncan's departure means agriculture secretary Tom Vilsack will be the sole remaining Cabinet-level secretary who has been with Obama since 2009, said CNN.