Biden’s meeting with the King family and other civil rights advocates came two days after Saturday’s racist attack in Jacksonville, Florida. Three black people were shot dead by a white man wearing a mask and firing a weapon emblazoned with a swastika. The shooter, who had also posted racist writings, killed himself.

Asked how he would stop hatred, Biden said: “By talking directly to the American people because I think the vast majority of the American people agree with this table,” referring to the civil rights advocates who were in the room with him. “But we have to understand, this is serious.”

Thousands gather in Washington 60 years after King’s ‘dream’ speech

“Yet there are those who are intentionally trying to divide us as a nation and I believe each of us has a duty, a duty to not allow factions to sever our unity,” said Harris, the first black person elected vice-president. “Our diversity is our strength and our unity is our power as a nation, and I do believe that we must be guided by knowing that we have so much more in common than what separates us.”

After the meeting, King’s son lamented the state of racial affairs in the US, saying: “we are at a very challenging and difficult time.”

“You would think America would be much further than it is,” he told reporters on the White House driveway. But he said that “when people come together, change can occur. And we must change this trajectory.”

Monday was 60 years since the March on Washington on August 28, 1963, which drew tens of thousands to the nation’s capital to advocate for civil rights, justice and freedom. It is where Reverend King delivered his famous “I Have a Dream” speech at the Lincoln Memorial.

The White House invited a broad group of civil rights leaders to the meeting, including Martin Luther King III, his wife, Arndrea Waters King, his sister Bernice King and the Reverend Al Sharpton, along with representatives from organisations representing Jews, Hispanics and Asian Americans, according to Sharpton’s National Action Network.

Biden also was to address a reception on Monday evening to mark the 60th anniversary of the Lawyers’ Committee for Civil Rights Under Law, a non-partisan, non-profit legal organisation that was established at Kennedy’s request to help advocate for racial justice.

In an opinion piece written for The Washington Post, Biden said the administration is working to advance King’s dream of a society in which people don’t judge others by their skin colour.

Biden said his policies have led to a drop in black unemployment, more small businesses being opened by black entrepreneurs and more black families covered by health insurance.

He’s given some US$7 billion to the network of historically black colleges and universities and has emphasised appointing black people to his Cabinet and White House staff, throughout the federal judiciary and to independent agencies like the Federal Reserve.

“For generations, black Americans haven’t always been fully included in our democracy or our economy, but by pure courage and heart, they have never given up pursuing the American dream,” Biden wrote.

White gunman driven by racial ‘hate’ kills 3 black people in Florida

He also referenced Saturday’s attack in Jacksonville, Florida.

“We must refuse to live in a country where black families going to the store or black students going to school live in fear of being gunned down because of the colour of their skin,” Biden wrote.

Biden’s meeting with King’s family and his remarks at the reception will give the president, who is running for re-election, an opportunity to appeal to black voters by talking about what he and the broader administration have done to help make their lives better.

But Biden has also struggled to fulfil key promises to black voters, perhaps the most loyal group in his political base. He kept a promise to put a black woman – the first to serve – on the Supreme Court, but has been unable to follow through on pledges to shore up voting rights or enact changes to policing to help stop violence against people of colour by police. Legislation on both issues has stalled in a divided Congress.

The 1963 March on Washington is still considered one of the greatest and most consequential racial justice demonstrations in US history.

The nonviolent protest attracted as many as 250,000 people to the Lincoln Memorial and provided momentum for Congress to pass landmark civil rights and voting rights legislation in the following years. King was assassinated in April 1968 in Memphis, Tennessee.

On Saturday, the same day as the shooting in Florida, thousands converged on the National Mall for a 60th anniversary commemoration.