US billionaire Mike Bloomberg has qualified for the upcoming Democratic presidential debate, marking the first time he will stand alongside the rivals that he has so far avoided by skipping the early voting states and using his personal fortune to define himself through television ads.

A new NPR/PBS NewsHour/Marist poll published Tuesday shows Bloomberg with 19 percent support nationally in the Democratic nominating contest.

The former New York City mayor, who launched his presidential campaign in November, will appear in Wednesday's debate in Las Vegas alongside former Vice President Joe Biden, Senators Bernie Sanders, Elizabeth Warren and Amy Klobuchar and former South Bend, Indiana, Mayor Pete Buttigieg. Fellow billionaire and philanthropist Tom Steyer is still hoping to qualify.

More:

Bloomberg's campaign said that it was seeing "a groundswell of support across the country" and that qualifying for Wednesday's debate "is the latest sign that Mike's plan and ability to defeat Donald Trump is resonating with more Americans."

"Mike is looking forward to joining the other Democratic candidates on stage and making the case for why he's the best candidate to defeat Donald Trump and unite the country," Bloomberg campaign manager Kevin Sheekey said in a statement.

Democratic presidential candidate Bernie Sanders, centre, speaks during a Democratic presidential primary debate [File: AP Photo/Patrick Semansky]

The Democratic National Committee recently changed its rules for how a candidate qualifies for the debate, opening the door for Bloomberg to be on stage and drawing the ire of some candidates who dropped out of the race for failing to make prior stages. The candidates were previously required to receive a certain number of campaign contributions to qualify, but Bloomberg, who is worth an estimated $60bn, is not taking donations.

The prime-time event will be a stark departure from Bloomberg's highly choreographed campaign. He has poured more than $300m into television advertising. While he's campaigned in more than two dozen states, he does not take questions from voters and delivers a standard stump speech that lasts fewer than 15 minutes, often reading from a teleprompter.

Bloomberg is likely to face far more direct fire in the debate. His fellow Democratic contenders have stepped up their attacks against him in recent days, decrying him for trying to "buy the election" and criticising his support of the "stop-and-frisk" tactic while mayor of New York City that led police to target mostly black and Hispanic men for searches.

Bloomberg has barely crossed paths on the trail with his fellow Democrats. He decided to skip the first four voting states of Iowa, New Hampshire, Nevada and South Carolina in favour of focusing on the 14 states that vote on March 3 and the contests that come afterwards.

He rarely mentions his rivals by name, though his campaign is centred on the idea that none of them can beat President Donald Trump. And Bloomberg, more than anyone, has predicated his campaign on a potential Biden collapse. He has been aggressive in targeting African-American voters in the South, a core demographic for Biden's campaign.

Former Vice President Joe Biden speaking to supporters at a campaign event in Hampton, New Hampshire [File: Elise Amendola/AP Photo]

Biden said he does not think "you can buy an election".

"I'm going to get a chance to debate him on everything from redlining to stop-and-frisk to a whole range of other things," Biden told reporters last week.

The poll released Tuesday shows Sanders leading in the Democratic primary contest, at 31 percent support nationally. After Bloomberg at 19 percent, Biden is at 15 percent, Warren at 12 percent, Klobuchar at 9 percent and Buttigieg at 8 percent. Steyer is at 2 percent, and Representative Tulsi Gabbard is at less than 1 percent, with 5 percent undecided.

The telephone survey of 527 Democrats and Democratic-leaning independents was conducted by the Marist Poll at the Marist Institute for Public Opinion. It has a margin of error of plus or minus 5.4 percentage points.