NAACP head Derrick Johnson, Jackson Mayor Chokwe Lumumba (D) and Rep. Bennie Thompson (D-Miss.) are set to hold a press conference in Jackson, Miss., on Saturday morning.
The civil rights advocates said their event was meant "to pay homage and recognition to those individuals who have dedicated their lives to the civil and human rights of Mississippians minus the presence of President Donald Trump."
Johnson and Rep. John Lewis (D-Ga.) announced this week that they would not attend the opening event for the Mississippi Civil Rights Museum after Trump said he would go.
"It’s going to be very difficult for me to be there and be on the same platform with him," Lewis told the Atlanta Journal-Constitution.
"I think his presence would make a mockery of everything that people tried to do to redeem the soul of America and to make this country better," he added.
White House spokesman Raj Shah told reporters aboard Air Force One en route to a campaign rally in Florida on Friday night that Trump's remarks at the museum will emphasize unity.