Staff Sergeant Ivan "Chip" Frederick, however, did not admit guilt to all of the elements of the five charges against him during the first of a two-day court martial on a military base at Baghdad's international airport.
He offered a rare insight into what went on in the detention centre where pictures of grinning US soldiers posing by a heap of naked Iraqi men taken earlier in the year sparked worldwide outrage.
The extent of the alleged abuse became even more apparent when one of the prisoners testified, describing being hit and humiliated to the point of wanting to die.
Referring to a photograph of a pyramid of seven inmates - one of the most notorious images from the Abu Ghraib outrage - Frederick, the highest-ranking soldier accused in the affair, said they were criminal suspects who had been hooded and their hands tied.
"We threw them in a pile," he told the trial judge.
"That's when Sergeant [Javal] Davis started jumping in the pile," he said referring to one of two other soldiers due to appear in court this week.
Frederick said Davis had been "sort of" laughing as he stomped on the prisoners' hands and feet, and admitted that he could have stopped the abuse.
"But I didn't," he said.
Instead, the military policeman joined in as the detainees were stripped and abused, punching one of them, he added.
"I stood him up and punched him in the chest. I was angry. They told me he was the ringleader who hit a female soldier in the face with a rock," said Frederick.
Frederick confessed to playing
an active role in the torture
The man slumped down and signalled for an inhaler so a medic was called, but the ordeal did not stop there.
The naked prisoners were lined up against a wall still with bags over their heads.
"I told one of them to masturbate," Frederick said.
He revealed that other soldiers embroiled in the scandal, including Private First Class Lynndie England and Corporal Charles Graner, were watching and taking pictures.
Frederick admitted that he thought his actions had been indecent and immoral.
When asked by Colonel James Pohl, the presiding judge, why he did it, the soldier responded: "Just to humiliate him ... it makes the army look bad."
In an emotional appearance, the prisoner who was humiliated and tortured by Frederick described scenes of terror and suffering at the jail.
"Just to humiliate him ... it makes the army look bad"
US soldier at Abu Ghraib prison
"I was crying. I wanted to kill myself," he told the judge before putting his head down on the witness stand, unable to continue with his story for a while.
Victim now suicidal
The Iraqi, whose identity was not released for security reasons, then described how after the abuse, the seven prisoners were taken to their cells, which were flooded with water, and told to sleep there - naked except for bags on their heads.
There were no beds or blankets, said the prisoner, who had been accused of stealing a car and rioting.
"I felt humiliated but I had nothing to kill myself with," he said.
Asked by the prosecutor whether he still felt this way, he said yes.
Just following procedure
Frederick said military intelligence and criminal interrogators set conditions for interrogation and that one Criminal Investigation Division official asked the military police who were guarding the prisoners to scare them.
The soldier said photos were taken
for souvenirs, not interrogation
He described how they put one prisoner on a box, attached wires to him so he thought he would be electrocuted if he fell, and took photographs.
Frederick admitted that he took pictures as souvenirs rather than to be used as an interrogation tool.
Davis and Graner are due to appear before a judge at Camp Victory later this week.
Testifying in the court martial, Captain Donald Reese, a military police commander at Abu Ghraib, said the CIA was involved in abusing detainees.
He said US civilian "OGA" officials - an acronym meaning
Other Government Agency reserved for the CIA - interrogated Iraqi inmates at night, when supervision at the prison was low.
One inmate, who CIA interrogators were depriving of sleep, was suffering from "panic attacks", he said.
"I was told it [nudity] was the actions of the military intelligence
community and it was an accepted practice"
Captain Donald Reese,
A military police commander
"They [CIA] came in at any time of day. They came in through the back door and put [prisoners] in one of the cells. We were told by OGA that they'd be back for them again later," Reese said via video link from the US on Wednesday.
Reese, the commander of the 372nd Military Police Company, said there were so many types of interrogators on the site it became difficult to keep track. He mentioned staff from the CIA, the FBI, military intelligence and military police.
"It was very confusing," he said. "Sometimes they wore civilian clothes, sometime military uniforms. And military intelligence had their name tags removed sometimes."
He said he had seen naked detainees being held at the prison shortly after arriving in October and wondered what on earth was going on. "Did you ask about the nudity?" Frederick's lawyer Gary Myers asked Reese in court.
"I was told it was the actions of the military intelligence community and it was an accepted practice," Reese replied.