US Defense Secretary Robert Gates acknowledged on Sunday it will be "tough" to close the US prison at Guantanamo Bay by a January deadline set by US President Barack Obama.
"It's going to be tough" for the Obama administration to meet the January 22 deadline to shut the camp condemned as a "legal black hole" by rights groups, Gates said.
But played down the importance of missing the deadline, saying he had supported setting the date as a way of pushing progress toward closing Guantanamo Bay, the US military prison in southern Cuba where 223 "war on terror" detainees remain.
"I actually was one of those who said we should (set a deadline) because I know enough from being around this town that if you don't put a deadline on something, you'll never move the bureaucracy," Gates told ABC television's This Week in an interview.
The Pentagon chief said he endorsed the decision to set a deadline during discussions in December with advisers when Obama was president-elect.
Obama signed an executive order in his first week of office in January vowing to close the facility within a year. Gates said he was unsure of how many prisoners would remain at Guantanamo on January 22.
In a separate interview with CNN, he recognised that meeting the deadline "has proven more complicated than anticipated" but suggested that a delay "shouldn't be a problem" so long as "you have a strong plan showing you're making progress in that direction."
A government team assigned the task of closing the prison has faced difficulties sifting through complex cases that include evidence possibly tainted by abuse. It also has struggled to persuade other countries to take some of the detainees.
Despite the unpopularity of Guantanamo abroad, Obama has faced a firestorm of opposition from both Republicans and his fellow Democrats in Congress to his plans to shutter the prison and move at least some of the detainees to US soil for trial or continued detention.
Three more Guantanamo detainees were transferred from Guantanamo, the Justice Department said on Saturday. The three were two unnamed prisoners thought to be Uzbeks who were sent to Ireland and a Yemeni man, Alla Ali Bin Ali Ahmed, who was returned to his native country.
Since Guantanamo was opened by former president George W Bush in January 2002, more than 550 detainees have been transferred from the controversial detention center, according to the Defense Department.
The Yemeni embassy in Washington issued a statement saying it welcomed "with enthusiasm, the release and transfer of its citizen."
"Yemen will continue its diplomatic dialogue with the United States government to repatriate the remaining Yemeni detainees" at Guantanamo, the statement late last week read.
According to US news reports, there are 90 Yemenis held prisoner at Guantanamo because the US State Department has not succeeded in negotiating a comprehensive repatriation and rehabilitation agreement with Sanaa.
Yemen will have to provide the United States with sufficient assurances that returnees will not engage in extremist acts of violence.
"I think Guantanamo is the best place for these hardened criminals. We don't want to put them in our general prison population where they have and will radicalize other prisoners," Senator Kit Bond, the top Republican on the Senate Intelligence Committee, told Fox News Sunday.
But Democratic Senator Dianne Feinstein disagreed, saying maximum-security US prisons were equipped to handle detainees from Guantanamo.
"No one is going to put these people in anyone's neighborhood, as some have tried to say," said Feinstein, who chairs the intelligence panel.
"In a maximum security prison, I don't worry about it, provided the prison is set up to accommodate it."