The US justice department has charged five Blackwater Worldwide security guards and is negotiating a plea deal with a sixth, according to people close to the case.

The move comes more than a year after a deadly shooting of 17 Iraqi civilians in Baghdad involving the private security firm that strained US-Iraqi relations.

Prosecutors reportedly ordered the five guards to surrender on Monday to the FBI to face manslaughter and assault charges, but details of where and precisely when were still being worked out Friday.

A federal grand jury in Washington has been hearing evidence in secret about the shooting by the Blackwater guards as they escorted a convoy of US diplomats through the Iraqi capital on September 16, 2007.

Blackwater, based in North Carolina, has said its guards acted lawfully and in self-defence after their motorcade came under fire in the chaotic incident.

It has co-operated in the investigation.

Most of the shooting

The investigation revealed that two guards did most of the shooting, the US TV channel ABC said.

The guards - US military veterans hired to protect US diplomats overseas - were responding to a car bombing when shooting erupted in a crowded Baghdad intersection.

The Iraqi government has said the guards deliberately killed the 17 civilians; an Iraqi investigation said there was no provocation for the guards to have opened fire.

After the shooting, the Iraqi government wanted to put the contractors under Iraqi legal jurisdiction.

Iraqis also were upset in April when the US state department renewed Blackwater's contract to protect US personnel in Baghdad.