WASHINGTON - Democratic incumbent President Joe Biden is projected to win the Democratic caucuses in Iowa and primaries in Virginia and Vermont, US media reported Tuesday.

The Associated Press (AP), NBC News and Fox News, among others, made the projection early Tuesday evening.

Democrats in Iowa sent out mail-in presidential preference cards and held in-person caucus meetings in January, but the party decided to announce the mail-in caucus results on Super Tuesday when over a dozen states hold primary elections.

In Virginia and Vermont, Biden easily beat author Marianne Williamson, who unsuspended her presidential campaign last week, and Congressman Dean Phillips, the two main challengers to the incumbent president.

Both Biden and Republican front-runner Donald Trump aim to secure a series of Super Tuesday wins but neither will be able to collect enough delegates to claim the title of "presumptive nominee".

Trump can clinch his party's presidential nomination on March 12 at the earliest and Biden on March 19, projected the AP.