An American civilian who was beheaded in Iraq had been visited three times by FBI agents while in the custody of Iraqi police, but he was never held by U.S. forces, contrary to claims by his family, U.S. officials in Baghdad said today.

The family of Nicholas Berg, 26, of West Chester, Pa., continued to insist today, however, that he had been had been held for 13 days by U.S. authorities in Iraq, a detention that family members said caused him to miss a scheduled departure from Iraq. Shortly after he was released, Berg was apparently captured by Islamic extremists.

President Bush, commenting on the murder for the first time, said today, "There is no justification for the brutal execution of Nicholas Berg -- no justification whatsoever." Addressing reporters on the South Lawn of the White House as he left for a speaking engagement, Bush said, "The actions of the terrorists who executed this man remind us of the nature of the few people who want to stop the advance of freedom in Iraq." He said the terrorists want to "shake our will," but that "we will complete our mission."

The young American businessman, who went to Iraq to seek work building radio towers, was decapitated with a large knife by masked captors who then held up his severed head before a video camera that recorded the scene. The video was posted Tuesday on the Web site of an Islamic militant group with ties to the al Qaeda terrorist network. The group attributed the savage murder to Abu Musab Zarqawi, a Jordanian terrorist who reportedly has established an organization in Iraq.

The body of Berg was found Saturday on a highway overpass outside Baghdad, and his family in the Philadelphia suburb was informed Monday by a U.S. consular officer that he had been decapitated.

His body was being repatriated to the United States today. An Air Force plane carrying it left Kuwait last night en route to Dover Air Force Base in Delaware, news agencies reported.

In a Baghdad news conference, Brig. Gen. Mark Kimmitt, the chief U.S. military spokesman in Iraq, said Berg's "grotesque and brutal murder" was an act of terrorism. He said Berg entered Iraq from Jordan for business purposes and had no affiliation with the U.S.-led occupation authority and, apparently, any private contractors working for the Coalition Provisional Authority.

Daniel Senor, a spokesman for the authority, said Berg was arrested in the northern city of Mosul on March 24 by Iraqi police, who apparently believed he might be involved in "suspicious activities." Senor said U.S. authorities were notified of the arrest and that the FBI visited him three times in Iraqi police custody. The FBI "determined that he was not involved with any criminal or terrorist activities," and Berg was released on April 6.

"It is my understanding he was advised to leave the country," Senor said. He said other details of Berg's movements are under investigation by the U.S. Army's Criminal Investigation Division and the FBI.

A State Department official in Washington told the Associated Press that Berg had turned down an invitation to fly out of Iraq. Spokeswoman Kelly Shannon said that a few days after he was released by Iraqi police, Berg spoke to a U.S. consular officer, who offered him a chance to fly back to the United States. "He told the consular officer that he planned to travel over land to Kuwait and would call the family from there," Shannon said.

Berg's family filed a lawsuit in federal court April 5 against the U.S. government, charging that Berg was being held by U.S. military authorities without due process. He was freed the following day.

Berg's father, Michael Berg, charged that the U.S. government bore some of the blame for the death of his son, who might have been able to leave Iraq before the violence there worsened if he had not been detained for so long, the Associated Press reported.

But Senor said today it was "incorrect" that Berg was ever held by U.S. authorities. "He was arrested and detained by Iraqi police," Senor said. "He was at no time under the jurisdiction or within the detention of coalition forces."

Kimmitt said there was no confirmation that Zarqawi, who has claimed responsibility for a number of suicide bombings and other attacks in Iraq, was involved in Berg's murder. Kimmitt said that in addition to the FBI visits, U.S. military police in the Mosul area monitored Berg's treatment at the Iraqi police station "to ensure that he was being fed and provided decent conditions."

Senor said, "He was not a U.S. government employee. He had no affiliation with the U.S. government, he had no affiliation with the coalition, and to our knowledge, he had no affiliation with Coalition Provisional Authority contractors." But, he said, Berg "still was an American citizen, and that's why we checked up on him. . . ."

Berg flew from New York to Amman, Jordan, on March 14 and traveled overland into Iraq, his family reported. It was his second visit to the country. But he was unable to drum up any business for his company, Prometheus Methods Tower Service, to inspect radio towers and provide parts and repair services.

He planned to leave Iraq March 30, but his detention in Mosul forced him to postpone his departure date, he reportedly informed his parents. He called his parents April 9 -- his last communication with them -- and checked out of a Baghdad hotel on April 10.

According to the Associated Press, Berg was a weight lifting enthusiast and amateur comedian who had traveled abroad to help people improve their lives. Among his trips was a visit to the West African country of Ghana, where he taught villagers to make bricks and returned emaciated because he gave away most of his food, the AP quoted his father as saying.

Michael Berg described his son as a Bush administration supporter who helped set up electronics equipment at the Republican National Convention in Philadelphia in 2000, AP reported. The father said his son was a practicing Jew and that his captors probably found that out, the agency said.

"If there was any doubt that they were going to kill him, that probably clinched it, I'm guessing," the AP quoted Michael Berg as saying.

In the video shown on the Islamic militant group's Web site, a masked captor read a statement in Arabic saying that the group had tried to exchange Berg for prisoners held by the U.S. military at Abu Ghraib prison west of Baghdad but had been rebuffed. U.S. authorities said they knew of no such offer.

The speaker in the video said before committing the murder that it was in revenge for the mistreatment of prisoners at Abu Ghraib and that more captives would be "slaughtered in this way."