The 'Raging Bull' actor, 80, who has previously said he wanted to punch Trump, 77, in the face, launched his latest blistering public attack on the former reality TV judge in a surprise speech outside the court where the former US president is standing trial in New York, before he clashed with a mob of Trump supporters.
De Niro, who has taken a leading role in the campaign to re-elect 81-year-old Democrat Joe Biden, said: "When Trump ran in 2016, it was like a joke... the Twin Towers fell just over here, just over there.
"This part of the city was like a ghost town, but we vowed we would not allow terrorists to change our way of life.
"I love this city. I don't want to destroy it. Donald Trump wants to destroy not only the city, but the country, and eventually he can destroy the world.
"I don't mean to scare you. No, no, wait - maybe I do mean to scare you.
"If Trump returns to the White House, you can kiss these freedoms goodbye that we all take for granted. And elections - forget about it. That's over, that's done.
"If he gets in, I can tell you right now, he will never leave".
The actor added Trump was a "clown" and "tyrant", before stating: "We have a second chance, and no one is laughing now. This is the time to stop him.
"If he gets in. I can tell you right now, he will never leave.
"Is that the country we want to live in? Do we want him running this country and saying 'I'm not leaving? I'm dictator for life'?
"The only way to preserve our freedoms and hold on to our humanity is to vote for Joe Biden for president".
The Oscar-winner also accused Trump of directing "an angry mob" to storm the US Capitol after his 2020 election defeat to Biden, adding the Republican "ran and hid in the White House" during the violence, which left dozens of police officers were injured.
De Niro was flanked during his press conference by retired officers Henry Dunn and Michael Fanone, who were wounded in the 6 January, 2021 insurrection.
Dunn is one of three officers who defended the Capitol and will campaign for Biden in key battleground states ahead of the president's first election debate against Trump, slated for 27 June.
Closing arguments began on Tuesday (28.05.24) in Trump's hush money trial, less than six months before the US presidential election.
Trump has spoken every day of his trial to TV news cameras inside the court, claiming the trial is a political attack against him, and De Niro's unexpected press conference seemed to be an effort to push back against Trump's dominance of the TV news channels.
It was held against a noisy backdrop of pro-Trump protesters' cheers and car alarms.
On his way back to his car after his press conference, De Niro clashed with Trump supporters who were yelling he was a "wannabe".
They also branded him a "paid sell-out" to the Democratic National Committee, "nobody" and a "little punk" whose films now "suck".
De Niro shouted back: "You're not going to intimidate. That's what Trump does.
"We are going to fight back. We're trying to be gentlemen in this world, the Democrats. You are gangsters. You are gangsters!"
When one Trump backer yelled: "You're washed up," De Niro hit back: "F*** you".