Bernie Sanders’ campaign has rejected calls from a leading Democrat to end its primary run following a string of losses to frontrunner Joe Biden.

House Majority Whip Jim Clyburn, a South Carolina congressman whose endorsement for Mr Biden helped revive the former vice president’s campaign, called for the cancellation of upcoming debates between the two Democratic rivals as Sanders’ path to victory appeared increasingly unlikely.

"I think when the night is over, Joe Biden will be the prohibitive favourite to win the Democratic nomination, and quite frankly, if the night ends the way it has begun, I think it is time for us to shut this primary down, it is time for us to cancel the rest of these debates," Mr Clyburn said as the first results came in on Tuesday evening.

"You don’t do anything but get yourself in trouble if you continue in this contest when it’s obvious that the numbers will not shake out for you," he told NPR.

The suggestion was quickly rebuffed by Briahna Joy Gray, national press secretary for the Sanders campaign.

“Let’s try democracy instead,” she tweeted in response.

In pictures: Bernie Sanders celebrates Nevada caucus win Show all 5 1 /5 In pictures: Bernie Sanders celebrates Nevada caucus win In pictures: Bernie Sanders celebrates Nevada caucus win Bernie Sanders and his wife Jane, triumphant at hearing of Nevada Caucus win. in San Antonio Texas on 22 February 2020 Reuters In pictures: Bernie Sanders celebrates Nevada caucus win Bernie Sanders embraces his wife Jane at rally in San Antonio Texas on 22 February 2020 REUTERS In pictures: Bernie Sanders celebrates Nevada caucus win U.S. Democratic presidential candidate Senator Bernie Sanders celebrates with his wife Jane after being declared the winner of the Nevada Caucus as he holds a campaign rally in San Antonio, Texas, U.S., February 22, 2020. REUTERS/Callaghan O'hare REUTERS In pictures: Bernie Sanders celebrates Nevada caucus win Bernie support raises sign and a thumbs-up to the news of Senator Sanders' win REUTERS In pictures: Bernie Sanders celebrates Nevada caucus win Bernie supporter cheer at the news of Sanders' win REUTERS

Mr Biden collected primary victories in Michigan, Missouri, Idaho and Mississippi, while Mr Sanders took North Dakota and was slightly ahead in Washington with 67 percent of votes counted.

With those victories in key states, Mr Biden widened his delegate lead over Mr Sanders to nearly 150. That lead may not seem insurmountable, but Mr Biden is heavily favoured in upcoming primaries due to take place later this month, among them Florida, Ohio, Illinois and Arizona. All of those states carry large delegate counts.

Rep. Clyburn was not the only party elder calling for Mr Sanders’ withdrawal from the race following Tuesday’s results, however. Democratic strategist James Carville, who played a key role in Bill Clinton’s successful presidential run, called for Democrats to “shut this puppy down” in order to unify the party and defeat Donald Trump.

“Let’s shut this puppy down, and let’s move on and worry about November. This thing is decided. There’s no reason to keep it going, not even a day longer,” he said on MSNBC.

"People will say things that you cannot overcome,” he warned.

As of Wednesday morning, the Sanders campaign showed no signs of backing down. The two Democratic rivals are due to debate each other on Sunday evening.

Ms Gray said of the upcoming clash: “I, for one, am extremely excited about this debate all the moderates are panicking about.”