The liberal New England senators remain interested in serving in Biden's cabinet, but even some of their allies recognise they face major political hurdles getting there.

Sensing disappointment, progressive leaders have reluctantly begun to express support for less-controversial alternatives.

Warren, whose political career has been defined by efforts to diminish the power of big banks, is the progressive movement's top choice for Treasury secretary.

Sanders, a self-described democratic socialist, reiterated his desire to serve as Biden's Labor secretary on Thursday, describing himself as particularly well-suited "to focus on the many crises facing working families in this country".

Whether he is included in Biden's cabinet or not, Sanders warned Biden not to freeze out progressives as he shapes his government.

"It seems to me pretty clear that progressive views need to be expressed within a Biden administration," Sanders told the Associated Press.

"It would be, for example, enormously insulting if Biden put together a 'team of rivals' - and there's some discussion that that's what he intends to do - which might include Republicans and conservative Democrats - but which ignored the progressive community. I think that would be very, very unfortunate."

In a best-case scenario for Democrats, the Senate would be divided 50-50 in January when the new Congress is sworn in, with vice President-elect Kamala Harris in position to break the tie.

But that's only if Democrats win both of Georgia's special elections on January 5.

Biden will be the first Democrat US president in modern times trying to set up a first-term administration without his party controlling the Senate, a rare dynamic that will play out before a bitterly divided country and a hyper-partisan legislature.

The more controversial potential nominees, Warren and Sanders among them, would likely struggle to win confirmation.

Australian Associated Press