The U.S. Marine sergeant accused of leading a massacre of 24 Iraqi civilians in Haditha pleaded guilty on Monday to dereliction of duty, ending the final prosecution stemming from a 2005 incident that brought international condemnation of U.S. troops.

Staff Sergeant Frank Wuterich, 31, entered his plea at Camp Pendleton Marine Corps base north of San Diego as part of a deal with military prosecutors in which more serious charges of involuntary manslaughter and aggravated assault were dismissed.

As part of his guilty plea, Wuterich accepted responsibility for providing negligent verbal instructions to the Marines under his command when he told them to shoot first and ask questions later, which resulted in the death of innocent civilians.

He faces a maximum sentence of three months of confinement, forfeiture of two-thirds of his pay for three months and a reduction in rank when he is sentenced on Tuesday, a Camp Pendleton spokesman said.

By pleading guilty to this charge, Staff Sergeant Wuterich has accepted responsibility for his actions, base spokesman Lt. Col. Joseph Kloppel said.

Any discharge process Wuterich may face will be separate from the plea and sentencing, Kloppel added.

Wuterich, 31, was accused of being the ringleader in a series of November 19, 2005, shooting and grenade attacks that left two dozen civilians dead in Haditha, a city west of Baghdad that was then a hotbed of insurgent activity.

The killings were portrayed by Iraqi witnesses as a massacre of unarmed civilians and brought international condemnation of the U.S. military.

Local witnesses claimed angry Marines had killed unarmed men, women, and children after a popular comrade, Lance Corporal Miguel TJ Terrazas, was killed by a roadside bomb.

'CAULDRON OF WAR'

Lawyers for the troops involved argued the deaths resulted from a fast-moving situation in which the Marines believed they were under enemy fire.

Wuterich was originally charged with murder in the case.

No one denies that the consequences of November 19, 2005 were tragic, least of all Staff Sgt. Frank Wuterich, his civilian defense attorney, Neal Puckett, said in a statement released shortly after the plea hearing.

But the fact of the matter is that he has now been totally exonerated of the homicide charges brought against him by the government and the media. For six years he has had his name dragged through the mud. Today, we hope, is the beginning of his redemption, the statement said.

Wuterich pleaded not guilty when the court-martial began in early January.

The proceedings were suspended last Wednesday by the military judge in the case, who ordered prosecutors and defense lawyers to seek a negotiated plea deal.

The trial resumed on Friday for one day, and the plea agreement was announced on Monday morning.

Many pundits from all walks of life will comment on Wuterich's purported guilt and most of these are people who have never been remotely associated with the challenges of combat action, Colonel Willard Buhl, a U.S. Marine Corps military fellow at the Council on Foreign Relations, told Reuters.

Marines know that they are the best trained and led military men and women in the world, Buhl said. But the cauldron of war is the most intense thing humans can experience and this case falls on the extreme end of that spectrum.

Buhl served in the same battalion and regiment as Wuterich, but never met him and was deployed in that unit prior to the events at Haditha that are at the centre of the case.

Six out of the eight Marines originally accused in the case had their charges dismissed by military judges, and a seventh was cleared of criminal wrongdoing.

Wuterich enlisted in the Marines after his 1998 graduation from high school, where he was an athletic honour-roll student and played with the marching band.

He was serving his second tour of duty in Iraq when the Haditha incident occurred.

(Editing by Dan Whitcomb, Steve Gorman and Paul Thomasch)