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Military and Justice Department officials told members of the Senate Judiciary Committee on Wednesday that major steps are being taken to protect the rights of prisoners at the terrorist detention center at Guantanamo Bay (search), Cuba, and to process their cases.

Detention "serves the vital military objectives of preventing captured combatants from rejoining the conflict and gathering intelligence to further the overall war effort, and to prevent additional attacks against our country," said Michael Wiggins, deputy associate attorney general.

The latest defense came after several critics suggested the facility be shut down. Committee chairman Arlen Specter, R-Pa., said the difficulty of processing non-state enemy combatants creates "a crazy quilt" under any analysis.

"Congress has its work cut out for it as we look at a very, very tough issue on how we handle detainees," said Specter. "At any rate, Congress hasn't acted."

But a leading Senate Democrat called the prison "an international embarrassment to our nation."

Sen. Patrick Leahy of Vermont, the senior Democrat on the panel, said if evidence supports terrorism or other criminal activity by the detainees, "then let's prosecute them. Let's bring the evidence forward."

Among those testifying are Brig. Gen. Thomas L. Hemingway of the Department of Defense's Office of Military Commissions (search) and Rear Adm. James M. McGarrah, who monitors enemy combatants in detention for the Navy.

McGarrah told the panel that of the 558 detainees given hearings at Guantanamo, 520 were "properly classified" as enemy combatants.

Of the remaining 38, he said, 23 have been released so far.

"Because of the highly unusual nature of the global War on Terror, and because we do not want to detain any person longer than necessary, we've taken this unprecedented and historic action to establish this process to permit enemy combatants to be heard while conflict is ongoing," McGarrah said.

Hemingway added: "America is at war. It is not a metaphorical war. It is as tangible as the blood, the rubble that littered the streets of Manhattan on Sept. 11, 2001."

Of the detainees, "We are holding them humanely," Hemingway said. "I think we can hold them as long as the conflict endures."

The prison at Guantanamo Bay (search), also known as Gitmo, has been at the center of controversy recently as some human rights groups and others allege mistreatment of prisoners there. Senators on both sides of the aisle have said that the U.S. naval base in Cuba has created an image problem for the United States that is hurting its reputation in the Arab world.

During Wednesday's hearing, Leahy questioned Defense Secretary Donald Rumsfeld's Tuesday assertion that the prison camp was an essential part of the U.S.-led War on Terror. "All of us know this war will not end in our lifetime," Leahy said.

"Guantanamo Bay is an international embarrassment to our nation, to our ideals and remains a festering threat to our security," he added.

Sen. Edward Kennedy, D-Mass., said the treatment of prisoners at Guantanamo stained the nation's reputation for human rights, inflamed the Muslim world and had become "a powerful recruiting tool for terrorists."

"Closing Guantanamo makes sense," Kennedy said, although earlier this week, he suggested that more issues need to be probed thoroughly before any decision is made whether to close the facility.

Rumsfeld was quick to point out that many of the terror suspects being held in Guantanamo Bay are close to Usama bin Laden (search) and, if given the chance, would rejoin the battlefield and try to kill Americans and other U.S. allies. Some even have, he said.

"The kind of people held at Guantanamo include terrorist trainers, bomb makers, extremist recruiters and financiers, bodyguards to Usama bin Laden and would-be suicide bombers — they're not common car thieves — they're believed to be trained killers," Rumsfeld told reporters during a Pentagon briefing Tuesday.

Wiggins told the committee that each Guantanamo detainee was given a formal hearing in front of a review panel to ensure they were all properly classified as enemy combatants.

But he said that the detainees were not being held "for criminal justice purposes, and [are] not part of our nation's criminal justice system."

"Detainees enjoy some constitutional rights," he said, adding it was hard to specify just which ones.

Gitmo Detainees Are 'Trained Killers'

On Tuesday, Rumsfeld noted that administrative review boards annually assess the potential threat and intelligence value of each detainee for possible release.

"Our goal as a country is to detain as few people as is possible and is safe," he said. "We prefer to return them to their country or origin if the country is capable and willing to manage them in the appropriate way."

Rumsfeld said U.S. taxpayers have already spent $100 million to build the facility, which he added is costing $90 million to $95 million a year to operate. "I don't know of any place [else] where we have infrastructure that's appropriate for this group of people," he added. "As long as there remains a need to keep terrorists from striking again, a facility will continue to be needed."

The White House backed Rumsfeld on Wednesday, with White House press secretary Scott McClellan saying the defense secretary was "talking for the administration" with his comments.

"There are no plans, as we have said, for closing or shutting down Guantanamo Bay at this time," McClellan said. "But we're always looking about how best to keep America safe and how to deal with these detainees."

A PR Problem for the U.S.

Some lawmakers argue that the United States has a public relations problem when it comes to how it treats prisoners of war.

"Yes, there is an image challenge that we have there ... [but] let's address the fundamental issues, let's not cut and run because of image problems," Senate Majority Leader Bill Frist, R-Tenn., said Tuesday.

"There is no doubt there is a problem there that exists. But I believe the problem is more a problem related to the disposition of prisoners there ... I think the key to this is to move the judicial process forward so these individuals will be tried rather than reside there in perpetuity," said Sen. John McCain, R-Ariz., who was a Vietnam POW.

Politicians of all stripes want investigations into allegations that U.S. troops mistreated foreign terrorism suspects. Meanwhile, Rep. Ellen Tauscher, D-Calif., and 23 co-sponsors on Tuesday introduced a bill to prevent detainee abuse. It mandates that the Pentagon share reports from the International Committee of the Red Cross (search) and other human rights groups about the treatment of detainees at U.S. prisons with Congress within 15 days of their receipt.

FOXNews.com's Liza Porteus and The Associated Press contributed to this report.