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.