Harris will speak on the anniversary of the deadly attacks, after Biden offered scathing criticism of Republican frontrunner Donald Trump's actions that day in a speech near Valley Forge, Pennsylvania on Friday.

The vice president will visit Myrtle Beach, South Carolina, to deliver the keynote address at the 7th Episcopal District AME Church Women's Missionary Society annual retreat.

"Three years ago today, on January 6, 2021, a mob invaded the United States Capitol. They used violence and fear to try to overturn the results of a free and fair election, and to overrule the votes of millions of Americans," Harris plans to say, according to excerpts from her remarks released by her office.

"On that day, we saw violence, chaos, and lawlessness, even though some so-called leaders still say it was a peaceful protest led by, quote, 'great patriots,'" the remarks say.

Biden credits South Carolina with catapulting him to the White House in 2020, and the state was moved to the top spot in the party's nominating calendar, ahead of Iowa and New Hampshire.

The AME, or African Methodist Episcopal church, formed in response to racial discrimination in an American Methodist church in the late 1700s, has thousands of congregations worldwide and several million members. Biden will speak at the Mother Emanuel AME in South Carolina on Monday, where nine members were killed by a white supremacist in 2015.

Although Biden is not facing serious competition for the Democratic presidential nomination, polls show he has lost some support from Black voters nationwide. A strong primary turnout in a state where the majority of Democratic voters are Black would calm fears about his electability among the party.

"Let us not throw up our hands. Instead, let us roll up our sleeves. We were born for a time such as this. We love our country," Harris says in the excerpts.

"We believe in the principles upon which we were founded. And guided by our faith, we are prepared to fight for those principles. With hope, with optimism, and with faith. When we fight, we win," she says in the remarks.

(Reporting by Steve Holland; Editing by Heather Timmons and Gerry Doyle)