Obama hopes to leave office with the prison shuttered, since he campaigned on a vow to close it and has argued that it serves as a recruiting tool for terrorists. On his second day in office, he signed an executive order to shut down the prison at Guantanamo, pledging to have it done within a year.
At the same time, other campaign promises to fully withdraw American troops from Iraq and Afghanistan now seem out of grasp. So officials are moving with greater urgency to act on one of the last items on his foreign policy agenda that could be achievable by the end of 2016. The prison houses alleged members of terrorist organizations captured by the U.S. overseas.
Difficulties finding a place to relocate detainees forced the president to abandon his original timeline. The majority of Guantanamo prisoners have been there for over a decade, dozens without being charged.
But continued opposition from Congress to closing the prison and moving the prisoners, plus a bureaucratic system that draws out the process for transferring prisoners from Guantanamo, makes final closure of the facility by January 2017 far from certain.
Over the summer, the Obama administration said it was finalizing a closure plan for submission to Congress, but months later it has not yet sent the final draft to lawmakers.
Military experts are still conducting site surveys of locations inside the United States where detainees could potentially be relocated. The sites include the military prison in Leavenworth, Kansas; the Naval Consolidated Brig in Charleston, South Carolina; and the federal Supermax prison in Florence, Colorado.
The White House said this week that it is awaiting information from those surveys to include in its plan to lawmakers.
Officials said the plan will call for speeding up transfers of roughly half of Guantanamo's population to their home countries or to other willing states. It will also include new security protocols to ensure detainees are kept from returning to terrorist activities once outside U.S. control.
Detainees that have been judged too dangerous for outside transfer -- with potential host countries refusing to take the risk of holding them -- would be moved to prisons inside the United States, either to be detained or brought to trial.
But that would require Congress to change a law banning any Guantanamo transfers into the U.S. -- an unlikely proposition, given that Republican lawmakers sought to impose even tougher restrictions on detainee transfers in the defense authorization measure that Obama vetoed on Thursday.
Many Republicans oppose closing Guantanamo because they think it's an important tool for America in its fight against terrorists and because of concerns about the danger of putting convicted foreign terrorists in American jails.
"This legislation specifically impedes our ability to close Guantanamo in a way I have repeatedly argued is counterproductive to our efforts to defeat terrorism around the world," Obama said during a rare public veto ceremony.
"Guantanamo is one of the premier mechanisms for jihadists to recruit," he said. "It's time for us to close it. It is outdated, it is expensive, it has been there for years, and we can do better in terms of keeping our people safe while ensuring we are consistent with our values."
Human rights groups have long criticized the U.S. military for a slew alleged abuses at the facility, including the practice of extended interrogations, sensory deprivation and forced shaving.
Detainees have protested the treatment and prolonged imprisonment with hunger strikes, which have resulted in forced feedings -- another practice condemned by human rights groups as well as the American Medical Association.
At least seven detainees have died in the prison.
A top U.S. military commander, however, defended their treatment Thursday.
"They are very, very well treated and always have been," SOUTHCOM Commander Gen. John Kelly told CNN en Espanol. "And most of the reporting on Guantanamo in terms of the treatment of the detainees over the years has been at best misinformed."