Washington, Jan 12
Six Democratic candidates have been invited to participate in the party's seventh presidential primary debate on January 14, the Democratic National Committee (DNC) and hosts have announced.

The candidates are former Vice President Joe Biden; former Mayor of South Bend, Indiana, Pete Buttigieg; Senators Amy Klobuchar, Bernie Sanders and Elizabeth Warren; and billionaire activist Tom Steyer, reports Xinhua news agency.

The debate, the seventh of a dozen scheduled for the Democratic Party's primary, will take place at Drake University in Des Moines, Iowa, and be moderated by CNN and The Des Moines Register.

Biden and Sanders will stand at centre stage that night, according to CNN. Warren will be to the left of Biden, and Buttigieg will be to the right of Sanders. Steyer will stand next to Warren, and Klobuchar will be next to Buttigieg.

The candidates qualified because they have received 5 per cent or more support in at least four polls or 7 per cent or more support in two polls in early-voting states and garnered donations from at least 225,000 unique donors, a criteria agreed by the DNS, CNN and The Des Moines Register.

The lineup has been the smallest, whitest, and least diverse to date in this election cycle, as there were no candidates of colour.

Entrepreneur Andrew Yang, a fast-rising candidate who nonetheless failed to meet polling thresholds to take part in the upcoming debate, unsuccessfully called for the DNC to commission more polling to make up for a lack of surveys over the holidays.

"If the DNC had only done their due diligence and commissioned polls in the early states, Andrew Yang would certainly be on the debate stage next week," campaign chief Nick Ryan said in an email to supporters on Saturday.

The announcement came a day after the release of The Des Moines Register/CNN poll on Friday, widely considered the most authoritative in Iowa.

Sanders is narrowly leading in Iowa, with the support of 20 per cent of likely Democratic caucus-goers, according to the poll. He's trailed closely by Warren, another progressive, who registered 17 per cent in the survey.

Buttigieg and Biden, who's leading comfortably in national polls and holding a wide lead among black voters, rounded out the top four, with 16 per cent and 15 per cent support, respectively.

Klobuchar notched 6 per cent in the poll, putting her in the fifth place, while Yang finished just below her, with a 5 per cent support.

The 2020 Iowa Caucuses are scheduled for next month, which will kick off the presidential nominating calendar.

There are currently 13 Democrats contending for the party's nomination to take on President Donald Trump on November 3.

6 Democratic candidates to appear in 7th presidential debate