Democratic presidential hopeful former vice president Joe Biden (center) arrives on stage with his wife Jill Biden and sister Valerie Biden Owens for a Super Tuesday event in Los Angeles on Tuesday. Photo: AFP

Joe Biden, counted out just days ago, took control of the race for the Democratic presidential nomination on Wednesday after racking up stunning primary victories over Bernie Sanders and earning the endorsement of deep-pocketed billionaire Michael Bloomberg.

President Donald Trump hailed the "incredible comeback" of the 77-year-old former vice president in the Super Tuesday contests and directed a stream of insults at Bloomberg after the fellow New Yorker ended his campaign.

"Those of you who have been knocked down, those of you who have been counted out - this is your campaign," Biden said in Los Angeles.

Sanders, 78, the leftist senator from Vermont, expressed confidence in his chances of winning the nomination despite being "disappointed" with his showing on Tuesday, when the centrist Biden won at least 10 of the 14 states at stake.

"We go forward basically neck and neck," Sanders told reporters in his hometown of Burlington, Vermont, where the self-described democratic socialist got his start in politics as mayor four decades ago.

In an interview with MSNBC's Rachel Maddow, Sanders warned it would not be easy.

"Do not underestimate Donald Trump. He'll have endless amounts of money because he doesn't believe in the rule of law. He will combine federal agencies with his own campaign. He has a loyal group of supporters, so it's not going to be so easy to beat him."

Meanwhile, Sanders said he had spoken with fellow progressive candidate Elizabeth Warren, and confirmed that the senator from Massachusetts was "assessing" her campaign following her poor performance on Super Tuesday.

The Washington Post reported that the Sanders and Warren camps were talking about uniting, should she withdraw from the campaign in the near future.

Biden, who is making his third White House bid after failed runs in 1988 and 2008, welcomed Bloomberg's backing in the contest for the spot on the Democratic ticket against the Republican incumbent in November.

AFP