US President Joe Biden said he would ask Congress to do more to hold social media companies accountable for spreading hate and asked Americans to speak out against racism and extremism during a summit at the White House.

"White supremacists will not have the last word," Mr Biden told the 'United We Stand' summit of bipartisan local leaders, experts and survivors.

Mr Biden said the US had long experienced a "through line of hate" against minority groups, one that had been given "too much oxygen" by politics and the media in recent years.

"It's so important that we keep hollering. It's so important for people to know that's not who we are."

The event also recognised communities that suffered hate-based attacks, including mass shootings at an LGBT+ nightclub in Orlando in 2016 and at a supermarket in Buffalo, New York, earlier this year, in which ten people were shot dead.

Hate crimes in the US hit a 12-year high in 2020 in the latest available data, the FBI said last year.

Mr Biden was introduced by Susan Bro, mother of Heather Heyer, who was killed during a white nationalist rally in Charlottesville, Virginia, in 2017.

"Her murder resonated around the world, but the hate did not begin or end there," Ms Bro said.

Participants gave Mr Biden a standing ovation when he said he would call on Congress to "get rid of special immunity for social media companies and impose much stronger transparency requirements on all of them".

The White House event comes just weeks after Mr Biden warned in a speech in Philadelphia that extremist Republicans are a threat to democracy.

Mr Biden addressed criticism that the speech was divisive saying, "we can't remain silent".

Mr Biden appealed for a united front against hate crimes and political violence in a speech building on his bid to present himself as champion of moderate values at a time of rising extremism.

"We have to face the good, the bad and the truth. That's what great nations do and we're a great nation.

"You must choose to be a nation of hope, unity and optimism or a nation of fear and division and hate."

It comes two weeks after Mr Biden delivered a fiery speech denouncing the "extreme ideology" of former president Donald Trump.

A White House official told reporters that this event, which featured a panel with both Republican and Democratic mayors, was not political and would "demonstrate that we can unite across partisan lines".

However, Republicans have painted Mr Biden as a divider for calling out supporters of Mr Trump, noting that the former president remains hugely popular with the party's voters.

Mr Biden defended himself in his White House speech.

"There are those who say that when we bring this up we divide the country," he said, adding that "silence is complicity."

Mr Biden announced a €1 billion push by philanthropists to build bridges among Americans of different backgrounds, and an initiative supported former Presidents Barack Obama, George W Bush, Bill Clinton and Gerald Ford.

Several big technology companies also joined in and YouTube said it was expanding its efforts to combat violent extremism by removing content glorifying violent acts for the purpose of inspiring others to commit harm, fundraise, or recruit.

Microsoft said it was expanding use of artificial intelligence and machine learning tools to detect credible threats of violence, and use gaming to build empathy.