Staff Sgt. Ivan L. "Chip" Frederick, the highest-ranking of eight soldiers charged with abusing detainees at Abu Ghraib prison last year, pleaded guilty Wednesday to taking part in the mistreatment, telling a military judge that he knew his actions were wrong at the time he committed them.

In a deal with Army prosecutors, Frederick, who was in charge of the night shift in the prison wing where detainees were abused, pleaded guilty to eight of 12 criminal counts, including a charge that he helped attach wires to a detainee with the intention of making him think he might be electrocuted. The picture of that detainee -- hooded, naked and standing on a box -- was one of several that stirred an international scandal when they surfaced six months ago.

Frederick, 38, told the judge, Col. James Pohl, that he knew he should not have been trying to scare the detainee. "I was wrong about what I did, and I shouldn't have done it," the Army reservist said. "I knew it was wrong at the time because I knew it was a form of abuse."

At the court-martial, Frederick testified that military intelligence and civilian interrogators "would tell us what conditions to set for them -- keep their clothes, give them cigarettes."

"You took this as your role as an MP to set conditions for detainees?" Pohl asked.

"Yes, your honor," Frederick replied.

A former Iraqi detainee, the first to testify publicly at a court-martial about the abuse, said Frederick punched him and forced him to masturbate in front of other detainees who were "crying and screaming." Army officials asked that the man's name, which was entered into the court record, not be disclosed to protect him.

"I was crying," the former detainee said during the court-martial at Camp Victory, a large Army installation near Baghdad International Airport. "I wanted to kill myself."

He paused and put his head down on the stand for several minutes. The man, who had been detained for allegedly stealing a car and participating in a riot, said he was forced to sleep naked in a cell flooded with water.

"I felt humiliated but I had nothing to kill myself," the former detainee said.

Frederick said an Army investigator responsible for interrogations encouraged him to abuse the detainee, saying he didn't care what was done to the prisoner "as long as you don't kill him."

Seven members of the Army's 372nd Military Police Company, based in Cresaptown, Md., have been charged in the scandal. Frederick and Spec. Jeremy C. Sivits have pleaded guilty. Sivits was sentenced in May to a year in prison; Frederick is expected to be sentenced this week and faces up to 18 years in prison.

An eighth soldier, Spec. Armin J. Cruz Jr., the only military intelligence soldier charged, pleaded guilty last month and was sentenced by Pohl to eight months in prison. Cruz was a reservist with the 325th Military Intelligence Battalion, based in Devens, Mass.

All three soldiers who pleaded guilty have agreed to testify against fellow soldiers in exchange for lighter sentences.

While Frederick's plea does not have any direct impact on pending cases, his testimony could be used at future courts-martial, possibly to bolster the argument by attorneys for other charged MPs that military intelligence interrogators encouraged the behavior that resulted in abuses.

The fact that Frederick was the most senior soldier involved in the abuses and that he accepted responsibility for taking part in them could carry even more weight in the pending cases. Lower-ranking soldiers facing criminal charges -- such as Pfc. Lynndie R. England, whose court-martial is scheduled to begin in January -- are expected to argue that they did what their superiors ordered them to do. England's attorneys have also suggested that the culture at Abu Ghraib encouraged and condoned such activities.

England's lead civilian attorney, Richard A. Hernandez, said he was pleased that Frederick entered a guilty plea because it made him available to testify at England's trial. He said he believed Frederick's testimony could only help his client. England's defense team has been arguing that she was following orders from higher-ranking soldiers at Abu Ghraib.

"The orders were passed down from above," Hernandez said. "This is what we have been saying all along."

Meanwhile, the husband of a kidnapped aid official appealed to his wife's captors on Wednesday on the al-Arabiya satellite television network.

"We are in Ramadan, the holy month," said Tahseen Ali Hassan, an Iraqi who is married to Margaret Hassan, director of operations in Iraq for CARE International, a relief group carrying out health and water projects in the country. "My wife has been in Iraq for 30 years to help the Iraqis. She loves Iraq. We appeal to the kidnappers, in the name of Islam, brotherhood and humanity, we ask them to release her. She is not involved in politics. She does only humanitarian projects."

In a telephone interview, Hassan said he had not eaten or slept since his wife was kidnapped on Tuesday morning. "I'm honestly shattered since they took Margaret," he said. "I'm shaking. I don't know what to do with myself."

CARE announced Wednesday that it was temporarily suspending its operations in Iraq.

Qasim Dawood, Iraq's minister of state, condemned the kidnapping, calling it a "crime against Islam and Iraqi traditions." He said that the government was doing everything it could to secure Hassan's release.

In a statement, he called the abduction of Hassan, who holds Irish, British and Iraqi citizenship, "a clear indication of the base and bad intents of the terrorists who call themselves mujaheddin, a clear insult to Islam and Iraq. This is all the more despicable coming during the holy month of Ramadan."

Also on Wednesday, one Iraqi child was killed and 11 U.S. soldiers with the 1st Infantry Division were wounded when a car bomb exploded near the center of Samarra.

The U.S. military said the soldiers were in stable condition and that the incident was under investigation. Samarra, about 65 miles north of Baghdad, was the focus of a U.S.-Iraqi assault on Oct. 1 that military officials said broke the grip of insurgents who had taken control of the town.

Despite the continuing violence, U.S. and Iraqi officials have pledged that national elections will take place by the end of January. Hoshyar Zebari, Iraq's interim foreign minister, said at a news conference that it was critically important to keep the elections on schedule "to show our commitment to democratic change."

But he criticized the United Nations for not playing a larger role in providing specialists to facilitate the process.

Correspondent Karl Vick and special correspondents Khalid Saffar and Omar Fekeiki in Baghdad and staff writer Josh White in Washington contributed to this report.

Staff Sgt. Ivan L. Frederick may testify in other cases of MPs.