WASHINGTON (CNN) -- Efforts to close the U.S. detention center at Guantanamo Bay, Cuba, are at "a standstill," Defense Secretary Robert Gates told a Senate subcommittee Tuesday.
"The brutally frank answer is that we're stuck, and we're stuck in several ways," Gates told the defense subcommittee of the Senate Appropriations Committee.
Human rights groups have long called for the facility to be closed, alleging that detainees endure numerous human rights violations amounting to torture.
CIA chief Michael Hayden admitted this year that the agency had used waterboarding, a controversial technique that simulates drowning, on three Guantanamo detainees.
Gates said that he favors closing the detention center, which currently holds about 270 detainees, but that a number of problems stand in the way.
For one, Gates said, there are about 70 detainees ready for release whose home governments either will not accept them or may free them after they return.
He referred to former Guantanamo detainee Abdullah Saleh al-Ajmi, who killed himself in a suicide attack last month in Mosul, Iraq, after being released from Guantanamo in 2005.
Al-Ajmi was not the first former detainee reported to have returned to the battlefield after leaving Guantanamo. Pentagon officials say that more than 10 people have been killed or captured in fighting after being released from the detention facility.
Gates said there were also several detainees who cannot be freed but who are also ineligible for prosecution under the military courts set up by the Bush administration. Gates did not elaborate on why those detainees would not be charged.
"What do you do with that irreducible 70 or 80, or whatever the number is, who you cannot let loose but will not be charged and will not be sent home?" Gates asked.
Furthermore, he said, there are lots of obstacles to overcome in order to send the detainees to U.S. prisons.
"We have a serious 'not in my backyard' problem. I haven't found anybody who wants these terrorists to be placed in a prison in their home state," he said.
Last week, a lawyer for several Guantanamo detainees said that a judge's decision could further delay efforts to try al Qaeda figures held at Guantanamo Bay.
A military judge ordered Brig. Gen. Thomas Hartmann, a Pentagon lawyer, to stay out of the case of Salim Ahmed Hamdan, Osama bin Laden's former driver and bodyguard, after ruling that he exerted improper influence on prosecutors trying the case.
Defense attorney Charles Swift said the ruling is likely to stall the case against Hamdan and other al Qaeda figures being tried in the Bush administration's military courts.
The Bush administration insists that it does not torture suspected terrorists during interrogations. The president said that top al Qaeda suspects had been subjected to "tough" but legal interrogation methods in prisons overseas.