A federal judge in Washington on Friday refused to further prolong a public-records case that has raised questions about Hillary Clinton's use of a private email server during her service as U.S. secretary of state during the Obama administration.

The plaintiffs in the lawsuit had urged District Judge Reggie Walton to allow "discovery" in an effort to find any additional records that might be related to an advertisement that the U.S. embassy in Islamabad produced that was titled "A Message from the President of the United States Barack Obama and Secretary of State Hillary Clinton."

Walton's order on Friday said the demand for additional discovery by the plaintiffs—Judicial Watch, the conservative advocacy group, brought the suit in 2012—was "speculative and insufficient to delay summary judgment briefing any further."