WASHINGTON — As white nationalists planned to gather in front of the White House on Sunday to mark the anniversary of last year’s violent rally in Charlottesville, Va., President Trump denounced “all types of racism,” but did not specifically condemn the supremacists.
“Riots in Charlottesville a year ago resulted in senseless death and division,” he wrote on Twitter on Saturday morning. “We must come together as a nation. I condemn all types of racism and acts of violence. Peace to ALL Americans!”
Mr. Trump’s general call for unity, as Washington braced for the possibility of violence between the white nationalists and counterdemonstrators, echoed his reluctance a year ago after the deadly Charlottesville rally to single out the supremacists for condemnation.
In what is seen as a defining mark of his presidency, he blamed “both sides” for the violence, eliciting widespread criticism for what was seen as drawing a moral equivalence between hate groups — some of whom supported his candidacy — and those who protested them.
Accusations of racism have shadowed Mr. Trump over his decades as a real estate mogul, reality television star and president. Those claims have been renewed in recent weeks as he has questioned the intelligence of prominent black people such as LeBron James and Representative Maxine Waters and criticized professional football players for kneeling during the national anthem.
In a new memoir, Omarosa Manigault Newman, a former White House adviser tasked with outreach to African-Americans, claims that the president regularly used a racial slur while he was the host of the show “Celebrity Apprentice,” though she never heard him say it herself. Asked by a reporter about the book on Saturday at his club in Bedminster, N.J., the president held a hand to his mouth, as if to whisper, and said: “Lowlife. She’s a lowlife.”
The rally on Sunday, called Unite the Right II, is scheduled to take over Lafayette Square for two hours in the evening. Officers from the United States Park Police and the Washington police department will erect a barrier separating the white nationalists and the thousands of counterprotesters who intend to oppose them.
The Unite the Right group plans to have up to 400 people at the rally, according to the permit it received from the National Park Service, though the number in attendance could be considerably smaller. An antiracism group, the Answer Coalition, was granted a permit in Lafayette Square for a group more than three times the size of Unite the Right’s. Other groups of counterprotesters have permits to gather elsewhere in the city.
Jason Kessler, who helped organize last year’s Charlottesville rally, is scheduled to speak to the crowd, as is David Duke, the former politician and Ku Klux Klan leader.
The Park Service granted a routine First Amendment demonstration permit to Mr. Kessler. “In anyone’s recollection, there has never been a First Amendment permit that’s been denied,” said Mike Litterst, a Park Service spokesman.
Last year in Charlottesville, neo-Nazis, Ku Klux Klansmen and other members of hate groups marched through the University of Virginia campus shouting anti-Semitic slogans, then fought with counterprotesters in the city streets. A man who espoused neo-Nazi views drove his vehicle into the counterdemonstators, killing a 32-year-old woman, Heather D. Heyer.
The chance of that kind of spontaneous mayhem has led to weeks of planning between Washington’s law enforcement agencies, which have developed proposals to guard marches leading to the rally and the rally itself, as well as deal with any confrontations that precede or follow it in the streets of Washington.
Sgt. James Dingeldein of the Park Police said his agency, the Washington police and the Park Service had met with Mr. Kessler and leaders of counterprotest groups to explain to them what is permissible on the grounds of the park. The Park Service has issued a detailed set of limits and prohibitions on items that can be brought in, banning some of the items that were wielded in Charlottesville.
“If there is potential for violence, it will be dealt with quickly,” Sergeant Dingeldein said. Mr. Kessler said last month that he would discourage those attending from acting violently.
Federal officials have expressed concern that violence could spill into downtown streets once the rally has dispersed and its participants may feel less inhibited. Sergeant Dingeldein said the police agencies had riot control teams that could be deployed.
James Murray, an assistant director in the Secret Service’s Office of Protective Operations, warned in a letter on Monday to the Park Service that some of the same counterprotesters who seized downtown streets at the presidential inauguration in January 2017 were also interested in Sunday’s demonstrations, and were “known to have engaged in violent and destructive activity.”
“Violence can commonly occur between highly charged groups of protesters and counterprotesters,” Mr. Murray wrote. Members of the sometimes violent movement known as antifa are expected to be among the counterprotesters on Sunday.
Muriel E. Bowser, the Washington mayor, activated the city’s emergency operations center on Thursday. Although no rally is planned in Charlottesville this weekend, Gov. Ralph Northam of Virginia declared a state of emergency. Police officers in Charlottesville had put up metal barriers by Saturday morning to cut off access to downtown streets.
“We have people coming to our city for the sole purpose of spewing hate,” Ms. Bowser said at a news conference on Thursday. “It didn’t make sense last year, and it doesn’t make sense now.”
A version of this article appears in print on , on Page A21 of the New York edition with the headline: Pre-Rally, Trump Issues General Call for Unity. Order Reprints | Today’s Paper | Subscribe