Robert De Niro has branded Donald Trump a "total monster".

The 'Killers of the Flower Moon' actor has urged Americans to vote for Joe Biden to stay in office at the upcoming presidential elections as letting the former 'Apprentice' star back into the White House would be a "nightmare".

Speaking on 'Real Time with Bill Maher', he said: “We wanna live in a world that we want to live in and enjoy living in, or live in a nightmare? Vote for Trump and you’ll get the nightmare, vote for Biden and we’ll be back to normalcy.

“I just don’t want to feel the way I did - and many of us did - the many months after the election in 2016, where we couldn’t believe that it happened. [Trump] is a total monster…

The 80-year-old actor can't understand why such a "hateful person" attracts as much support as he does.

He said: “I don’t understand it. I guess they get behind that kind of logic, they wanna [mess] with people, screw them, because they’re unhappy about something. He’s such a mean, nasty, hateful person.”

And the 'Goodfellas' star insisted he would "never" play the former president in biopic because he has no "redeemable" qualities.

He ranted: “I’d never play him as an actor because I can’t see any good in him. Nothing. Nothing at all. Nothing redeemable in him."

De Niro is convinced something would happen to him because of his stance if Trump gets reelected.

He said: “If he wins the election, you won’t be on this show anymore. He’ll come looking for me. There’ll be things that happen that none of us could imagine.

"That's what happens in that kind of a dictatorship, which is what he says, let's believe him, take him at his word."

He went on to brand the 77-year-old Republican a "sociopathic, psychopathic, malignant narcissist."

He added: “The bottom line is Biden’s our guy. He represents what this country’s supposed to be about.”

In response, Trump branded the 'Taxi Driver' actor a "stupid-sounding guy".

He wrote on his Truth Social platform: "Robert DeNiro has a terminal case of Trump Derangement Syndrome. Such a stupid sounding guy, a low IQ individual!(sic)"

This isn't the first time the pair have locked horns.

At the Gotham Awards in November, De Niro branded Trump a liar.

He said: “The former president lied to us more than 30,000 times during his four years in office, and he’s keeping up the pace with his current campaign of retribution.

“With all of his lies, he can’t hide his soul. He attacks the weak, destroys the gifts of nature and shows his disrespect for example using Pocahontas as a slur.”

In response, Trump branded the actor a "total loser".

He wrote on Truth Social: “Robert De Niro, whose acting talents have greatly diminished, with his reputation now shot, must even use a teleprompter for his foul and disgusting language, so disrespectful to our Country.

"He has become unwatchable both in movies, and with the FOOLS that destroyed the Academy Awards, bringing them from one of the top shows in the Country to a Low Rated afterthought.

"He should focus on his life, which is a mess, rather than the lives of others. He has become a total loser, as the World watches, waits, and laughs!”