WASHINGTON (Reuters) - U.S. Vice President Joe Biden eased past Vermont Senator Bernie Sanders in a national poll of voters about their preferences for a 2016 Democratic presidential candidate, according to media reports on Wednesday.

Hillary Clinton still led the field but with a reduced margin in the Monmouth University poll released on Tuesday. The former U.S. secretary of state had 42 percent support, down from 52 percent in August, while Biden had 22 percent backing and Sanders 20 percent. Biden, who has not said yet said whether he will seek the candidacy, had 12 percent support last month.

Biden's favorability rating rose to 71 percent from 67 percent to match Clinton's, compared with 41 percent for Sanders, the poll showed.

The poll of 1,009 adults, including 339 voters who said they were Democrats or Democratic-leaning, was conducted from Aug. 31 to Sept. 2, and had a margin of error of plus or minus 5.3 percentage points, the Wall Street Journal reported.

(This story corrects Clinton's title to former secretary of state)

(Reporting by Eric Walsh; Editing by Nick Zieminski)