Manchester (United States) (AFP) - Former US vice president Joe Biden drew criticism Sunday after he called a woman a "lying dog-faced pony soldier" at a campaign event in New Hampshire.

In an exchange that was widely shared on social media, 21-year-old Georgia college student Madison Moore asked the presidential hopeful to explain his poor performance in the Iowa caucus last week.

"It's a good question," replied Biden, whose status as national frontrunner for the Democratic nomination was shaken by a damaging fourth-place showing in Iowa's caucuses.

"Have you ever been to a caucus?" he asked the Mercer University student, who nodded.

"No, you haven't," Biden said. "You're a lying, dog-faced pony soldier."

Biden's campaign press secretary Remi Yamamoto tweeted the comment was a joke: "It's from a John Wayne movie and he's made it plenty of times before."

But the remark still drew criticism online, with many Twitter users saying the remark was not funny.

"If he can't handle a simple question from one of his own supporters, how can Joe Biden possibly take on Donald Trump one on one for six months?" tweeted Donald Trump Jr, the US president's son.

Moore told The Washington Post it was "totally irrelevant whether I've been to a caucus or not."

"Joe Biden has been performing incredibly poorly in this race. His inability to answer a simple question from a nobody college student like me only exacerbates that reality," she said.