A judge on Tuesday granted US prosecutors' request for trial delay as it considers whether to seek the death penalty for a white man accused of killing nine parishioners last summer at a historic black church in Charleston, South Carolina, in what prosecutors say was a hate crime.

District Judge Richard Gergel urged the federal government to make a decision soon on whether they would pursue the death penalty for Dylann Roof, 22, who plans to plead guilty if he will not be facing the possibility of execution. Gergel said he could set a trial date at some point in the interest of a speedy trial.

"There are victims here," Gergel said. "They have a right to put this behind them."

Roof, who faces 33 federal hate crime and firearms charges, is accused of opening fire during a June 17 Bible study at Emanuel African Methodist Episcopal Church in a crime that sparked a fierce social debate about race and gun control in the United States.

Assistant US Attorney Jay Richardson said he understood the Justice Department deliberations on whether to seek the death penalty for Roof had reached the desk of US Attorney General Loretta Lynch, who will announce the decision.

"This is obviously a very important decision and one that's being taken quite deliberately," Richardson said.

Roof's attorney, David Bruck, said if the death penalty is ruled out, there would be no need for a trial because Roof would plead guilty.

Gergel also had delayed Roof's trial in February at the request of his defence, which needed more time to prepare. The Justice Department also was still considering the death penalty.

The Justice Department declined further comment on Tuesday.

Some family members of victims and a survivor of the shootings attended Tuesday's hearing but Roof did not.

Roof had been linked to white supremacist views and Lynch has said the federal charges against him are based on evidence he targeted his victims because of their race, obstructing their exercise of religion.

South Carolina prosecutors are seeking the death penalty for Roof when he is scheduled to go on trial for murder on July 11.

In a related case, defence attorneys and prosecutors said they could be ready by mid-summer for the trial of Roof's friend, Joseph Meek, charged with concealing knowledge of a crime and lying to an FBI agent after the shooting. A trial date was not set.