Hillary Clinton has hit out at her former Democratic presidential rival Bernie Sanders, saying "nobody likes him, nobody wants to work with him" in an interview ahead of a new four-hour documentary on the former senator and first lady's life.

Key points: Hillary Clinton wouldn't confirm if she'd support or campaign for Senator Sanders if he won the nomination to face Donald Trump later this year

Hillary Clinton wouldn't confirm if she'd support or campaign for Senator Sanders if he won the nomination to face Donald Trump later this year Mrs Clinton beat Senator Sanders to be the 2016 Democratic presidential nominee. Senator Sanders is still in the running for the 2020 nomination

Mrs Clinton beat Senator Sanders to be the 2016 Democratic presidential nominee. Senator Sanders is still in the running for the 2020 nomination The film called Hillary will premiere at Sundance this weekend

According to The Hollywood Reporter, she says in the film: "He was in Congress for years. He had one senator support him. Nobody likes him, nobody wants to work with him, he got nothing done."

"He was a career politician. It's all just baloney and I feel so bad that people got sucked into it."

Mrs Clinton was promoting the Hillary documentary, which is set to premiere at the Sundance film festival this weekend before airing on US streaming service Hulu, and told the magazine her frank assessment still held.

She also would not confirm if she would support and campaign for Senator Sanders if he won the 2020 Democratic nomination, and pointed to the "culture around him".

Senator Sanders says his wife likes him. ( Reuters: Yuri Gripas )

"It's his prominent supporters. It's his online Bernie Bros and their relentless attacks on lots of his competitors, particularly the women," she said in the interview.

"I really hope people are paying attention to that because it should be worrisome that he has permitted this culture — not only permitted, [he] seems to really be very much supporting it.

"I don't think we want to go down that road again where you campaign by insult and attack and maybe you try to get some distance from it, but you either don't know what your campaign and supporters are doing or you're just giving them a wink and you want them to go after Kamala [Harris] or after Elizabeth [Warren]."

Tensions between Senator Sanders and Senator Warren have increased in recent weeks, after he allegedly said to her that a woman could not win the US presidential election.

It is something he has denied saying, but it marked a turning point in the Democratic race, as the pair had previously described themselves as friends.

Outside today's impeachment trial, reporters asked Senator Sanders about Mrs Clinton, and he responded: "On a good day, my wife likes me."

He would not be drawn further on her comments and said Mrs Clinton was "entitled to her point of view" but he was focused on the trial.

Hard road for Clinton over Sanders

Mrs Clinton went up against Donald Trump after defeating Senator Sanders for the 2016 Democratic nomination.

But it was a hard-fought campaign between the Democratic pair.

Senator Sanders offered his long-awaited formal endorsement of Mrs Clinton in July, after weeks of talks between the two camps and a month after she claimed victory in June.

Several thousand protesters, many of them "Berners" or Senator Sanders supporters, demonstrated outside the Democratic National Convention in late July and some even said they would prefer to vote for Mr Trump.

Mrs Clinton eventually lost to Mr Trump, something she later said was a "hard thing to accept."

The new documentary interviews both former presidents Bill Clinton and Barack Obama, and appears to delve into some of Mrs Clinton's struggles, including the Monica Lewinsky affair and Mr Clinton's impeachment and the leak of the 2016 Clinton campaign emails after Russia-linked hackers stole the Democrats' emails.

When promoting the film late last week, Mrs Clinton tweeted: "I've got the kind of life you can't make up."