Washington DC - President Joe Biden is trying to shore up his support among vital Black voters with a days-long series of events starting Thursday, including a visit to the former university of civil rights icon Martin Luther King.

Democrat Biden relied on African-American voters to help him beat Donald Trump in 2020, but some polls show they are increasingly deserting him ahead of November's rematch with the Republican.

On Thursday, Biden (81) marked the 70th anniversary of a famous Supreme Court ruling that overturned racial segregation in schools by meeting with key figures in the case in the Oval Office.

They included Adrienne Jennings Bennett, one of the plaintiffs in the 1954 Brown v. Board of Education case that proved a milestone for the US civil rights movement, and Cheryl Brown Henderson, a daughter of plaintiff Oliver Brown.

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Biden "recognized that back in the 40s and 50s ... the folks that you see here were taking a risk when they signed up to be part of this case," Henderson said after the meeting.

On Friday, Biden visited the Smithsonian's National Museum of African American History and Culture in Washington to give remarks to celebrate the anniversary of the Brown decision.

Later on Friday, Biden and Vice President Kamala Harris – the first Black, South Asian, and female "veep" in US history – will meet leaders from nine historically Black sororities and fraternities.

Biden is honoring "the legacy of those who paved the way for progress and hard-fought rights for Black Americans," said White House Press Secretary Karine Jean-Pierre.

"He will also highlight his vision for how we must continue to build on these freedoms," added Jean-Pierre, who is the first Black person to serve in the role.

Then, on Sunday, Biden will address students at the historically Black Morehouse College in Atlanta, Georgia, whose most famous former student is civil rights leader King.

Biden has a bust of King in the Oval Office in a sign of his support for racial equality, which he frequently contrasts with what he says is racially insensitive and anti-immigrant language by his rival Trump.

His visit to Morehouse is politically sensitive, however, as campuses and graduation ceremonies have recently been disrupted by widespread protests against Biden's support for Israel's war in Gaza.

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A senior White House official recently met students and faculty members at Morehouse to discuss objections to Biden delivering the commencement address, NBC News reported.

Biden's outreach to Black voters comes days after a New York Times/Siena poll showed that in addition to trailing Trump in several key battleground states, he is also losing ground with African Americans.

Trump is winning more than 20% of Black voters in the poll – which would be the highest level of Black support for a Republican presidential candidate since the Civil Rights Act was enacted in 1964, The New York Times said.

Several other polls have also shown Biden's support lagging among Black voters.

But a participant in Thursday's White House gathering, Derrick Johnson, president of the country's major civil rights organization NAACP, disputed the narrative that there has been "an erosion" of support among Black voters and said polls have been wrong in several recent elections.

"I hope that the American public recognizes in order for us to remain a leading democracy we must participate at the highest level," he said.

In 2020, Black voters were overwhelmingly loyal to the Democratic Party, with 92% voting for Biden and only 8% for Trump, according to the Pew Research Center.