WASHINGTON — Leaders in Washington, D.C., are preparing for what could be a contentious and trying day Sunday when the organizer of last year’s deadly white-supremacist rally in Charlottesville, Va., holds an anniversary gathering with up to 400 supporters in Lafayette Square across from the White House.

As many as 1,500 counterprotesters are expected at Lafayette Square and more at two nearby parks, setting up a possible volatile showdown.

Unlike in Charlottesville, where police allowed the opposing factions to clash in what turned into a bloody melee, Washington Police Chief Peter Newsham said Thursday that the goal ‘‘will be to keep the two groups separate.’’

On Wednesday, Virginia Governor Ralph Northam and the city of Charlottesville declared a state of emergency to deter violence from any impromptu rallies. Officials said the declaration would streamline operations this weekend while also allocating $2 million in state funds.

In last year’s rally, one woman died and more than a dozen people were injured after a man plowed his car into a crowd of counterprotesters.

Washington Post