WASHINGTON  - US President Barack Obama, fresh from re-election and facing a new clash with Congress, got back to work Thursday, with an important item on his to-do list, stocking his new cabinet.

Obama is expected to lose his heavyweights including Treasury Secretary Tim Geithner, Secretary of State Hillary Clinton and Defense Secretary Leon Panetta, for most if not all of his second four-year term.

The president will also likely have to make changes to his White House staff with some senior aides, exhausted by a crisis-strewn four years, expected to move on and others shifting to different administration jobs.

Speculation is already rife about who will replace Clinton, who has reiterated that she wants to reclaim a private life put on hold by decades in the spotlight of top level politics.

Clinton has said she has no interest in another White House race, but the campaign blitz for Obama by her husband former president Bill Clinton, and the power couple’s passion for politics, has sparked renewed spec ulation. Until Clinton makes her final decision known, the Democratic Party’s other possible 2016 presidential candidates will likely hold their fire, as the former first lady would be a prohibitive favorite if she did run.

UN ambassador Susan Rice, who has been close to Obama for years, has long been seen as a likely replacement for Clinton at the State Department, despite being caught up in the furor over the raid in the US consulate in Benghazi.

Another possible contender is John Kerry, chairman of the Senate Foreign Relations Committee, whose stock rose in Obama world after he played Republican nominee Mitt Romney in Obama’s practice dry runs for the presidential debates.

Rice would be the second African American woman to hold the post after Condoleezza Rice, to whom she is not related. She is known at the United Nations for an assertive manner and not shy about pounding home the US point of view.

A report in Russia’s Kommersant newspaper Thursday said that Moscow, with whom Rice has clashed heatedly over Syria, would prefer to see Kerry get the job, at a sensitive time between Obama and restored Russian President Vladimir Putin.

“It would be more difficult for Moscow to work with Washington” if Rice became Secretary of State, the unnamed Russian official was quoted as saying.

Kerry would have to step down from the Senate, however, and there is concern that his Massachusetts perch could fall prey to Republican Scott Brown, who lost a race with Democrat Elizabeth Warren for the state’s other Senate seat. White House sources said that the usual timetable for replacing cabinet members - in plenty of time for confirmation by the Senate after the presidential inauguration in January - could slip this time.

Geithner and Panetta are key figures in the year-end budget and tax showdown looming with Republicans, and may not move on until the so called “fiscal cliff” drama is resolved.

Some insiders talk about White House chief of staff Jacob Lew, himself a budget specialist, as a possible successor for Geithner while others speculate that Obama may reach for someone with business credentials to improve his shaky standing with the corporate world.

Panetta is expected to leave the administration at some point, but did not serve for the full four-year first term, having taken over just last year from Robert Gates, a holdover from the previous Bush administration.

Also known as a budget specialist, Panetta may stay in place until expected spending reductions are factored in to the Pentagon’s budgetary plan to return to his walnut farm in California’s Carmel Valley.

The current favorite to succeed him is Michele Flournoy, who served as under secretary of defense for policy early in Obama’s first term.

Her appointment may appeal to Obama’s sense of history as she would be the first woman to hold the role.

Should Flournoy not get the job, some defense analysts think that the current deputy defense secretary Ashton Carter could be in the frame.

There may also be other cabinet departures. It is unclear whether Attorney General Eric Holder, a close associate of Obama who has had a bruising from Republicans, will stay on.

Education Secretary Arne Duncan is expected to remain in place to pilot through Congress Obama’s reform program, likely a highlight of his second term agenda.

Obama may also have some shuffling to do at the White House, especially if Lew moves to Treasury. His political guru David Plouffe is expected to leave and there may be other high profile departures.

The president sparked speculation on Tuesday when he said he wanted to sit down with Romney to work out how they could take the country forward.

Obama’s first term “Team of Rivals” approach of choosing former political foes like Clinton, modeled on that of his hero Abraham Lincoln, could apply in Romney’s case, perhaps in a job like Commerce Secretary.

However, it is unclear whether Romney would be prepared to swallow his pride and work for the man who vanquished him in a bitter White House campaign.