Former Vice President Joe Biden made his long-expected 2020 announcement in a video Thursday, declaring the 2020 election a "battle for the soul of this nation."

Over images of white supremacist violence in Charlottesville, Virginia, Biden cited President Donald Trump's characterization of some of the white supremacists as "fine people."

"If we give Donald Trump four years in the White House, he will forever and fundamentally alter the character of this nation, who we are, and I cannot stand by and watch that happen," Biden said in the video.

"The core values of this nation, our standing in the world, our very democracy, everything that has made America America is at stake," Biden said. "That's why today I'm announcing my candidacy for president of the United States."

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Former Vice President Joe Biden has announced his candidacy for the US presidency, striking a notably dark tone in a video published early Thursday.

In the three-minute video, which featured images of white supremacists marching in Charlottesville, Virginia, he framed the 2020 presidential election as a fight for the "soul of this nation."

In a 6 a.m. tweet that included the video, Biden said: "The core values of this nation... our standing in the world... our very democracy...everything that has made America -- America --is at stake. That's why today I'm announcing my candidacy for President of the United States."

In the video, which included the words quoted in the tweet, he cited President Donald Trump's remarks after the violent August 2017 white nationalist protests in Charlottesville, Virginia, in which the president refused to unequivocally condemn the torch-bearing, swastika-wielding marchers.

In the video, Biden shared images of white supremacists marching in Charlottesville, Virginia. Joe Biden

"The president of the United States assigned a moral equivalence between those spreading hate, and those with the courage to stand against it," Biden said. "And in that moment, I knew the threat to this nation was unlike any I'd ever seen in my lifetime."

Biden declared America as being locked in "a battle for the soul of this nation."

"I believe that history will look back, on four years of this president, and all he embraces, as an aberrant moment in time," he added. "But if we give Donald Trump four years in the White House, he will forever and fundamentally alter the character of this nation, who we are, and I cannot stand by and watch that happen."

"Folks, America is an idea, an idea that is stronger than any army, bigger than any ocean, more powerful than any dictator and tyrant," he added. "It gives hope to the most desperate people on earth — it guarantees that everyone is treated with dignity and gives hate no safe harbor."

Biden, who was widely expected to run, enters the race leading polls of Democrats who have announced their candidacy in 2020.

While the crowded Democratic primary is expected to be competitive, however, his video largely positions himself in opposition to Trump, focusing on one of the most controversial episodes of the Trump presidency in drawing a clear line between the sometimes racially inflammatory nationalism of the Trump White House and a vision of a diverse America championed by Biden.

At the August 2017 rallies in Charlottesville, an anti-racism protester named Heather Heyer was killed by a white nationalist after hundreds of white nationalists, KKK members, and neo-Nazis had gathered to protest the removal of a Confederate monument.

Trump drew widespread bipartisan and international condemnation when he later declared that the racists among the groups' ranks included some "very fine people."