Barack Obama, the US president, has named his longtime foreign policy aide, Denis McDonough, as his new White House chief of staff, part of a major overhaul within his senior team.
The announcement of the appointment came on Friday at a ceremony in the White House's ornate East Room.
McDonough had been widely tipped to fill the vacancy created by Jack Lew's nomination as Treasury secretary. He has been serving as a deputy national security adviser. In his new role, considered one of Washington's most influential, he will stay mostly behind the scenes.
The chief of staff acts as the gatekeeper to the Oval Office, a co-ordinator of domestic and foreign policymaking.
In more than half a dozen other high-level staff changes, Obama also moved White House communications director Dan Pfeiffer to the job of senior adviser and replaced Pfeiffer with his deputy, Jennifer Palmieri.
Obama lauded McDonough as "one of my closest and most trusted advisers".
'Reaching across the aisle'
The appointment holds true to Obama's pattern of selecting confidantes and allies who are shuffled within his inner circle for his second-term.
McDonough, whose expertise lies in foreign policy, started his career with Obama when he was a freshman US Senator from Illinois and just beginning his rapid ascent on the national political scene.
He worked on Obama's 2008 presidential campaign and became a senior aide at the National Security Council when the president took office. He also served as foreign policy adviser to former Senate Democratic leader Tom Daschle.
"Denis has played a key role in every major national security decision of my presidency: ending the war in Iraq, winding down the war in Afghanistan, and from our response to natural disasters around the world like Haiti and the tsunami in Japan, to the repeal of 'Don't Ask Don't Tell,'" Obama said.
Critics have raised concerns over McDonough's lack of background in domestic policy, and say that may prove a handicap for him with fiscal matters, gun control and immigration shaping up as Obama's top priorities.
But McDonough's experience as a congressional staffer, and the close contacts he retains on Capitol Hill, are viewed as a plus.
Four days after laying out an ambitious liberal agenda in his second inaugural address, Obama said: "Denis understands the importance of reaching across the aisle to deliver results for the American people."