"This has become the greatest propaganda tool that exists for recruiting of terrorists around the world. And it is unnecessary to be in that position," said Senator Joseph Biden, a Delaware Democrat.
A Pentagon report released Friday detailed incidents in which US guards at Guantanamo desecrated the Quran. Last month, Amnesty International called the detention center for alleged terrorists "the gulag of our time," a charge Defence Secretary Donald Rumsfeld dismissed as "reprehensible".
The chairman of the Senate Judiciary Committee, Republican Senator Arlen Specter of Pennsylvania, plans hearings this month on the treatment of foreign terrorism suspects at the prison camp.
Biden, the top Democrat on the Senate Foreign Relations Committee, proposed that an independent commission take a look at Guantanamo and make recommendations.
"But the end result is, I think we should end up shutting it down, moving those prisoners," he told ABC's "This Week" television programme.
"Those that we have reason to keep, keep. And those we don't, let go."
He added, "I think more Americans are in jeopardy as a consequence of the perception that exists worldwide with its existence than if there were no Gitmo."
There are about 540 detainees at Guantanamo Bay. Some have been there more than three years without being charged with a crime. Most were captured on the battlefields of Afghanistan in 2001 and 2002 and were sent to Guantanamo
Bay in hope of extracting useful intelligence about the al-Qaida network.
William Schulz, director of Amnesty International USA, defended the group's earlier characterisation of Guantanamo Bay and other US detention facilities as gulags, but
acknowledged that "this is not an exact or a literal analogy".
He said there are differences, particularly in size and scope, between what goes on at US prisons and those run by the former Soviet Union.
"But there are some similarities," he insisted on Fox News Sunday.
Schulz likens the Guantanamo
facility to a Soviet gulag
"The United States is maintaining an archipelago of prisons around the world, many of them secret prisons into which people are being literally disappeared - held in indefinite incommunicado detention without access to lawyers or a judicial system or to their families.
"And in some cases, at least, we know that they are being mistreated, abused, tortured and even killed."
"And those are similar at least in character if not in size to what happened in the gulag and in many other prison systems in world history," he added.