Joe Biden accused election rival Donald Trump of suppressing diversity Friday, as the US president stepped up efforts to shore up support among Black voters ahead of November's election.

In a speech at the National Museum of African American History and Culture in Washington, the 81-year-old Democrat said the "extreme" Republican and his allies were trying to "erase history."

"My predecessor and his extreme MAGA friends are now going after diversity, equity and inclusion all across America," said Biden, referring to Trump's "Make America Great Again" movement.

"They want a country for some, not for all," he said at the museum, which was opened in 2016 by Barack Obama, America's first Black president, and has since become a Washington landmark.

Biden also criticized the "extreme" US Supreme Court which, with three judges appointed by Trump, has issued a string of controversial rulings on abortion, voting rights and diversity.

The speech was the latest in a series of events this week that officially mark the 70th anniversary of a US Supreme Court ruling that ended racial segregation in schools -- but which are also part of a major outreach to Black voters.

The veteran Democrat relied on African American voters to help him beat Trump in 2020, but some polls show those same voters are increasingly deserting him ahead of November's rematch with the Republican.

On Thursday in the Oval Office, Biden welcomed key figures and relatives of plaintiffs in the 1954 Brown v. Board of Education case that proved a milestone for the US civil rights movement.

Later Friday, Biden and Vice President Kamala Harris -- the first Black, South Asian and female vice president in US history -- will meet leaders from the "Divine Nine" historically Black college sororities and fraternities.

On Sunday, Biden will address graduating students at the historically Black Morehouse College in Atlanta, Georgia, where legendary US civil rights leader Martin Luther King studied.

Biden will then travel to Detroit where he will address the NAACP, the nation's top civil rights group.

"We are meeting Black voters where they are," Trey Baker, senior advisor to the Biden campaign, said in an email.

"After Donald Trump failed us, no administration has delivered for Black America like President Biden and Vice President Harris."