US Vice-President Joe Biden says the United States government will appeal against a court ruling dismissing manslaughter charges in the Blackwater shootings case.
A federal judge on 31 December dismissed all charges against five Blackwater security guards over the killing of 17 Iraqis in Baghdad on 16 September, 2007.
District Judge Ricardo Urbina said the Justice Department had used inadmissible evidence.
Five guards had all pleaded not guilty to manslaughter. A sixth admitted killing at least one Iraqi.
The BBC reports the ruling provoked anger in Iraq and the Iraqi government began collecting signatures for a class action lawsuit on behalf of people killed or wounded in incidents involving Blackwater.
Mr Biden said in Baghdad on Saturday the dismissal of the Blackwater charges was just that and not an acquittal.
Expressing "personal regret" over the shootings, Mr Biden said the Justice Department will file an appeal against the court's decision this week.