US author Marianne Williamson ends presidential run

US author Marianne Williamson said she is ending her bid for the Democratic Party's presidential nomination.

"With caucuses and primaries now about to begin, however, we will not be able to garner enough votes in the election to elevate our conservation any more than it is now," Williamson said in a message to supporters on Friday, Xinhua news agency reported.

"The primaries might be tightly contested among the top contenders, and I don't want to get in the way of a progressive candidate winning any of them," she said. "As of today, therefore, I'm suspending my campaign."

The announcement was widely expected after Williamson laid off her entire staff earlier this month.

A long-shot contender, Williamson officially launched her presidential campaign about a year ago and has campaigned on a politics of conscience, along with a number of progressive policies.

But the 67-year-old has struggled in national polls and has not qualified for a primary debate since last summer.

Williamson's exit shrank the Democratic primary field to 13 candidates.

Former US Vice President Joe Biden, a moderate, and progressive US Senators Bernie Sanders and Elizabeth Warren, are leading in the field, according to national polls.

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