A "high-value" detainee was hidden from Red Cross inspectors in Iraq on the orders of Defense Secretary Donald Rumsfeld (search), U.S. officials told Fox News.

The prisoner's situation, as first reported by U.S. News and World Report on Monday, was described as the result of a directive issued from the top American commander in Iraq, Lt. Gen. Ricardo Sanchez (search). However, the order to hide the detainee, described by officials as a terrorist, came from the Pentagon at the request of outgoing CIA chief George Tenet, Fox News has learned.

Military police were instructed to keep the detainee, referred to as "Prisoner XXX," out of sight of the International Committee of the Red Cross (search).

"XXX" was held in U.S. custody but not issued an "INS" number used by the coalition and the ICRC for tracking prisoners in Iraq, senior Defense officials said. "XXX" was also isolated and heavily guarded at Camp Cropper beginning last November, according to U.S. News.

The detainee's presence was kept so secret, in fact, that he "fell through the cracks" and blended into the larger prisoner population, officials said.

The ICRC has complained of prisoner abuses at Camp Cropper, a facility housing high-value detainees located near the Baghdad airport.

"XXX" is alleged to be a senior member of the Al Qaeda (search )-affiliated group Ansar al-Islam. After his capture, intelligence and military officers quickly determined he was valuable as an information source.

"He knew Ansar al-Islam's leadership structure, he knew their training techniques and he knew the locations of their camps and some of their operatives," one official said.

U.S. officials disputed any accusations that the military's handling of "XXX" was illegal, stating that a detainee who represents a direct threat to coalition forces does not have to be registered with the ICRC "right away."

"The Geneva Convention does not require that someone like this be immediately registered," one official said. "This guy was involved in terrorist activity in Iraq, and was involved in planning attacks on coalition forces."

But in a report on prison abuses in Iraq released last month, Army Maj. Gen. Antonio M. Taguba (search) stated that holding such "ghost detainees" was "deceptive, contrary to Army Doctrine, and in violation of international law."

And since the release earlier this month of confidential memos in which Justice Department lawyers argued Taliban and Al Qaeda fighters did not merit Geneva protections, the Bush Administration has stepped away from those assertions.

On Wednesday, the Senate voted to reaffirm Geneva protections for suspects in the War on Terror.

The Defense Department told the Associated Press that keeping "XXX" from the ICRC was a mistake.

"The ICRC should have been notified about the detainee earlier," Defense Department spokesman Bryan Whitman said on Wednesday night. "We should have taken steps, and we have taken the necessary steps to rectify the situation."

He added that the prisoner had been treated humanely.

It is unclear what the status of "XXX" is now or whether he has provided useful intelligence. The official said "XXX" was taken to Camp Cropper on the advice of the Justice Department after having initially been flown out of Iraq to an "undisclosed location." But the detainee "got lost in the system" almost as soon as he was returned to Iraq, and he was not interrogated again — despite having undergone intense questioning at the unknown location.

"We didn't talk to him again," an intelligence official said.

But when asked if they made requests for access to "XXX," CIA officials said they made some inquiries that were not answered. Some military officials disputed this, insisting they received no such queries.

In other developments, the Army said Gen. Paul J. Kern, commanding general of the U.S. Matériel Command, would oversee alleged misconduct by personnel in the 205th Military Intelligence Brigade, which is assigned to Abu Ghraib. Kern replaces Sanchez, who has recused himself from that role and will leave his command as part of a scheduled rotation.

Fox News' Ian McCaleb, Bret Baier and Jane Roh contributed to this report.