In an interview with The Guardian, actor Robert De Niro referred to President Donald Trump as a "real racist" and "white supremacist."

De Niro, who tends to refrain from public commentary, has been a vocal critic of the president.

In October, he was one of several public figures who received a pipe bomb from an extreme Trump supporter.

The actor has been criticized for lobbing insults at Trump, but he doubled down in The Guardian interview, saying Democrats have to be " more aggressive."

"Con artist," "pig," "blowhard," "buffoon" — all are terms used by Robert De Niro to describe President Donald Trump.

In a recent interview with The Guardian, De Niro doubled down on his longstanding criticism of the president, calling Trump him a "real racist" and "white supremacist."

"When you see someone like [Trump] becoming president, I thought, well, OK, let's see what he does — maybe he'll change. But he just got worse," said De Niro. "It showed me that he is a real racist. I thought maybe as a New Yorker he understands the diversity in the city but he's as bad as I thought he was before — and much worse."

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In October, De Niro was one of many public figures who received a pipe bomb from an extreme Trump supporter. The bomb was intercepted, and the culprit later arrested.

The comments represent De Niro's harshest denunciation of the president thus far. Ahead of the 2016 presidential election, the actor released a video calling Trump "a national disaster" and "an embarrassment to this country."

"I'd like to punch him in the face," De Niro said.

Trump in return has called De Niro a "low IQ individual" who received "too many shots to the head."

De Niro told The Guardian he would never represent Trump on screen. Getty

Now, the actor said he fears for his children growing up in Trump's America.

"One of my kids is gay, and he worries about being treated a certain way," he told The Guardian.

When asked whether he considers Trump a fascist, De Niro responded: "I guess that's what it leads to. If he had his way, we'd wind up in a very bad state in this country. I mean, the way I understand it, they laughed at Hitler. They all look funny. Hitler looked funny, Mussolini looked funny and other dictators and despots look funny."

De Niro's abrasive language has been criticized by members of the public, including New York Times columnist Frank Bruni, who argue that angry tirades simply mirror Trump's behavior.

For De Niro, it's part of his opposition strategy.

"Democrats have to be more aggressive," he told The Guardian. "You have to fight fire with fire."

According to the actor, Trump's most effective challenger in the 2020 election will be "strong enough to out-mouth him."

He pointed to former Texas congressman Beto O'Rourke, Democratic nominee for Georgia governor Stacey Abrams, and Democratic nominee for Florida governor Andrew Gillum, as politicians who might fit the bill. All three candidates lost in the 2018 midterm elections.

Though De Niro is worried about Trump paving the way for a politician with "the same values as he has but able to get much further and do more damage," he's also optimistic about the future.

"There has to be a way for people to come together and work it out and help the people who are in pain now in certain parts of the country," he told The Guardian, adding: "It ain't over till it's over as far as I'm concerned."