A former security contractor for the US firm Blackwater, whose murder conviction for a deadly 2007 Baghdad shooting was overturned last August, is to face a fresh trial.

Federal prosecutors said Nicholas Slatten, who was originally found guilty of first-degree murder, will face retrial as early as May, The Washington Post reported.

Slatten was part of a Blackwater Worldwide security detail that opened fire on civilians at a bustling traffic circle in the Iraqi capital in September 2007, killing 14 people and sparking international outrage.

He and three other former Blackwater guards were found guilty of murder in 2014, but the appeals court ruled this year that Slatten's conviction be thrown out, arguing that he should have faced a separate trial from his co-defendants.

Slatten, 33, had been accused of opening fire first during the incident, killing the driver of a van that had stopped near the Blackwater motorcade on Nisour Square in Baghdad.

But the appeals court ruled that since another of the accused had confessed to opening fire first, Slatten's conviction could not stand and that he should face a retrial on his own.

The US contractors shot at civilians, including women and children, with sniper rifles, machine guns and grenade launchers, killing at least 14 and wounding 17 others -- a slaughter that caused fury even in war-ravaged Iraq.

Relatives of the slain called for the four US guards to be executed.

Federal prosecutors in the US capital expect the trial to last around six weeks and to call around 50 witnesses, including more than a dozen Iraqis, the Post said.

The first hearing to set a trial date will take place on December 14, when officials will also decide on whether to release Slatten from a federal prison in Florida, where he has been serving a life sentence.

source: AFP