Democratic US presidential contender Bernie Sanders will stay in the White House race despite suffering a series of sweeping losses to frontrunner Joe Biden.

Mr Sanders acknowledged he was falling behind Mr Biden in the count of delegates needed to win the nomination, but said he was committed to the overarching goal of defeating Republican Donald Trump in November’s general election.

“On Sunday night, in the first one-on-one debate of this campaign, the American people will have the opportunity to see which candidate is best positioned to accomplish that goal,” he told reporters on Wednesday, referring to a scheduled debate with Mr Biden.

Mr Biden on Tuesday notched decisive primary victories in Michigan and three other states, taking a big step toward the party’s nomination to take on Mr Trump in November and casting doubt on the future of Mr Sanders’ fading White House bid.

Mr Sanders – who won in North Dakota but had hoped for an upset victory in the key state of Michigan to boost his flagging chances – was forced to cancel an election night rally in Cleveland, Ohio, due to concerns over the coronavirus.

The losses on Tuesday, coming after a series of sweeping Biden wins in last week’s Super Tuesday contests in 14 states, put Mr Sanders in a deeper hole in the delegate count.

Bernie Sanders speaks at a rally at Michigan University on March 8. Photo: AAP

But Mr Sanders said his anti-corporate economic agenda was winning the ideological battle and gaining support from young people who are the country’s future.

He said many Democratic voters still believe Mr Biden has the best chance of beating Mr Trump.

“While our campaign has won the ideological debate, we are losing the debate over electability,” he said.

Mr Biden has already begun to look ahead to the November election, calling for party unity and making an appeal to supporters of Mr Sanders.

“We share a common goal, and together we are going to defeat Donald Trump,” Mr Biden said in Philadelphia on Tuesday night, thanking Mr Sanders and his supporters for their energy and passion.

Just two weeks ago, Mr Sanders was seen as the frontrunner after an impressive win in Nevada in mid-February, while Mr Biden and the other moderate candidates continued to split the vote of the party’s centrists.

-AAP