Barack Obama, the US president-elect, has said repeatedly that he will shut down the prison camp at Guantanamo Bay in Cuba and is now faced with decisions about how to proceed.
Rights groups have urged Obama to move swiftly once he begins his White House term in January.
The detention and treatment of prisoners held at the US facility has been widely condemned by international rights groups and the UN and EU.
It has held more than 750 captives from around the world since opening in 2002, including many who were captured during the US "war on terror" that followed the attacks on the US of September 11, 2001.
Around 250 prisoners remain in the camp - most held without charge or trial - including 50 or so that have been cleared for release but cannot be returned to their home countries, the US government says, for fear of torture and persecution.
Two, including Osama bin Laden's former driver, have already faced full military tribunals, set up by the Bush administration to try the detainees, but widely condemned as unfair by rights groups.
Aides to Obama say he remains committed to closing Guantanamo and trying the remaining detainees.
"President-Elect Obama said throughout his campaign that the legal framework at Guantanamo has failed to successfully and swiftly prosecute terrorists, and he shares the broad bipartisan belief that Guantanamo should be closed," Denis McDonough, an advisor to Obama on foreign policy, said in a statement on Monday.
There are several options now on the table for the new administration.
1. Trying detainees using a new US legal system
Obama has considered proposing a new court system to try the Guantanamo detainees and has appointed a committee to decide how such a court would operate, recent media reports have said.
|The US has faced widespread criticism over
its treatement of detainees [GALLO/GETTY]
How specifically that system would operate remains unclear.
"There is no process in place to make that decision until his [Obama's] national security and legal teams are assembled," McDonough said.
But the idea of setting up a separate legal system for the detainees has already drawn some criticism, and invited comparisons to the military tribunals set up by the Bush administration.
"There would be concern about establishing a completely new system," Adam Schiff, a Democratic member of the House of Representatives Judiciary Committee and former federal prosecutor, said.
"And in the sense that establishing a regimen of detention that includes American citizens and foreign nationals that takes place on US soil and departs from the criminal justice system - trying to establish that would be very difficult."
2. Criminal trials in the US
Obama aides have also said Guantanamo's remaining detainees could be prosecuted in federal criminal courts.
Doing so in the US would grant the detainees legal rights equivalent to those of citizens, thus creating a host of problems for prosecutors.
|More than 750 prisoners have been held at the detention centre since 2002 [GALLO/GETTY]
Evidence gathered through military interrogation or from intelligence sources could be thrown out.
Defendents would also have the right to confront witnesses, which means undercover CIA officers or informants might have to take the stand, jeopardising their identities and revealing classified intelligence tactics.
The idea of bringing alleged terrorists onto US soil has also proved controversial.
Last year, the US senate overwhelmingly passed a non-binding bill opposing bringing detainees to the United States.
John Cornyn, a Republican senate judiciary committee member, says it would be a "colossal mistake to treat terrorism as a mere crime".
"It would be a stunning disappointment if one of the new administration's first priorities is to give foreign terror suspects captured on the battlefield the same legal rights and protections as American citizens accused of crimes,'' he said.
3. Trials in the US military court-martial system
Use of the US military's court-martial system is another possible option to try Guantanamo detainees.
|Could the US use its own military justice system
to try detainees? [GALLO/GETTY]
"The court martial system could be adapted very easily by congress - I think that's by far the better option," Scott Silliman, a law professor at Duke University and director of the Center on Law, Ethics and National Security, told Al Jazeera.
A US federal trial, like the case brought against Zacarias Moussaoui, who was convicted of conspiring to kill US citizens in the September 11 attacks, could be drawn out over several years.
However, courts-martial, which unlike federal trials can take place outside the US, but maintain a higher standard of evidence than that of the current military tribunals used by the Bush administration.
But critics have also said that the higher standard of evidence could create problems for the prosecuting teams similar to that in criminal trials.
Silliman, however, says the US has much to gain from the system, in terms of credibility, for holding detainees to the same standards as its own military forces.
For the detainees which the government maintains no evidence of criminality, Obama advisers told the Associated Press news agency on Monday that they would probably be returned to the countries where they were captured for continued detention or rehabilitation.
The outgoing administration contends this is easier said than done.
"We've tried very hard to explain to people how complicated it is," Dana Perino, a spokeswoman for the White House, says. "When you pick up people off the battlefield that have a terrorist background, it's not just so easy to let them go."
Some governments have denied that the Guantanamo prisoners are in fact their citizens, while others have been reluctant to agree to US requests to imprison or monitor former Guantanamo detainees.
The Bush administration says talks with Yemen for the release of around 90 Yemeni detainees into a rehabilitation programme have so far been fruitless.
5. Resettlement in other countries
At least 50 of Guantanamo's inmates have already been cleared for release but the US government says they cannot be returned to their home countries for fear of torture and persecution.
|Human Rights groups have called for a swift closure of Guantanamo Bay [AFP]
The US state department and international human rights groups have urged third-party countries to accept these Guantanamo prisoners.
In Berlin on Monday, five rights groups issued a joint call to European governments to grant humanitarian resettlement and protection to detainees from China, Libya, Russia, Tunisia, and Uzbekistan, among others.
"This would have a double effect: helping to end the ordeal of an individual unlawfully held in violation of his human rights, and helping end the international human rights scandal that is Guantanamo," Daniel Gorevan, who manages Amnesty International's "Counter Terror with Justice" campaign, said.
Analysts have said international governments might be more willing to negotiate on this issue with an Obama administration because the president-elect has spoken out against unilateral US action, and is less likely to have as strict requirements.
6. Keeping Guantanamo open
The likelihood of keeping the Guantanamo Bay detention facility open is an apparently a slim one in part, because of the negative publicity the Obama administration would receive.
The facility has been condemned by the UN, the EU, and numerous human rights groups, and many in the US argue that the camp is also a liability.
Even George Bush acknowledged in 2006 he would "like to close" it.
"Guantanamo Bay, for most people is a lightning rod for everything that's wrong with the United States," Silliman says. "I'm not sure Obama would be able to back away from his campaign pledge."
Were it to remain open, the US congress would be likely to have to pass a new law to keep the detainees there, and push through humanitarian and legal changes.
Another alternative is for the US to work with other countries to create jointly-operated detention facilities.
Whatever the plan the new administration pursues, Silliman says Obama isn't likely to push through changes on January 21 - his first day in office.
"We should not expect it to take place in the first couple of weeks of his administration, or even in the first couple months," he says.
"All of this is going to take time."