Joe Biden considering presidential run: Report

US Vice President Joseph Biden has begun to explore a possible presidential campaign, a media report said.

According to a report in The New York Times on Saturday, Biden's associates have already started to contact Democratic leaders and donors who have so far not endorsed Hillary Clinton or who have become increasingly concerned about odds of a successful run by the Clinton camp, Xinhua news agency reported.

Quoting one longtime support of Biden, the newspaper report said the vice president has been "deeply moved" by his deceased son's desire for him to run.

Meanwhile, one columnist of The New York Times wrote that Biden had already been holding meetings at his house, "talking to friends, family and donors about jumping in to challenge Mrs. Clinton" in Iowa and New Hampshire, two early-voting states.

If confirmed, Biden's entry would pose a direct threat to Clinton, who so far has been an undisputable front-runner of the Democratic field.

Though starting with a strong momentum, favourability rating for Clinton dipped recently as the former Secretary of State was grappling with negative news coverage, including her controversial practice of exclusively using personal email account and server while working as the US top diplomat.

According to the latest Quinnipiac poll released on Thursday, 57 percent of voters regarded Clinton as not honest and trustworthy, and 52 percent said that Clinton did not care about their needs or problems, in spite of the candidate's devotion of a fair amount of time since April to convincing ordinary Americans that she understood their struggle.

By contrast, the same poll found that Biden's favourability rating reached its peak in seven years with 49 percent, with 58 percent saying he cares about them.