WASHINGTON (Reuters) - The Bush administration has intensified efforts to send more security detainees from Guantanamo Bay to their own countries but hopes are very dim of closing the prison by year-end, senior U.S. officials say.

U.S. Navy guards walk inside fencing of Camp VI, the maximum security detention facility for terrorism suspects at the U.S. Naval Base at Guantanamo Bay, Cuba, July 23, 2008. The U.S. military invited news media members to view the facility on Wednesday. Picture taken on July 23, 2008. REUTERS/Randall Mikkelsen

A host of legal and practical problems have stalled moves to close the controversial prison at a U.S. naval base in Cuba, which opened in January 2002 to house terrorism suspects caught in President George W. Bush’s declared war against terrorism.

Of about 255 detainees now in Guantanamo, government agencies say 60 to 80 face special military tribunals. About 60 are in the process of being sent back to their own countries. The future of the remaining 115 or so is uncertain as there is not enough evidence to charge them and they are deemed too dangerous to send home.

“No one wants to release the next Mohamed Atta,” said one U.S. defense official, referring to one of the hijackers of a plane flown into the World Trade Center on September 11, 2001.

Senior officials from the Pentagon, the State Department, the White House and Justice Department all said despite a wish to close it, Guantanamo would likely be an issue for the next president following the November U.S. presidential election.

Both candidates -- Republican Sen. John McCain and Democratic Sen. Barack Obama -- want it closed.

The creation of the remote prison tarnished America’s image and human rights groups say it has damaged U.S. credibility. More than 500 prisoners have been released but most of the remainder have been confined for years without charges.

Bush’s National Security Council spokesman Gordon Johndroe said the president wanted to see Guantanamo shuttered but keeping America safe was his key concern.

“The number one priority is to make sure the worst terrorists of the world are given justice and that is a process that is not going to be completed by the end of the year.”

“For others cleared for release we want to make sure their home countries will put proper mechanisms in place to ensure they don’t return to terrorism and that no one is returned to a country that would potentially torture then,” Johndroe said.

DASH TO FINISH

In recent months, the State Department has been racing to get deals with more than half a dozen countries for the return of scores of detainees, seeking security assurances as well as guarantees the prisoners would be treated humanely.

During a visit to four North African countries this month -- Libya, Tunisia, Algeria and Morocco -- Secretary of State Condoleezza Rice made clear the only way to close Guantanamo was to start emptying it and nations must cooperate.

“We have really kicked our efforts into overdrive,” said a senior U.S. official of the State Department’s efforts.

More than one-third of the prisoners left are from Yemen and the State Department is trying to reach an arrangement with that government, but talks are progressing slowly.

“It is very easy for critics to say, ‘Close Guantanamo.’ But what do you do with these 100 Yemenis?” said the official.

The senior official, who spoke on condition he was not named, rejected claims by some human rights groups that the Bush administration was prepared to turn a blind eye to human rights abuses in order to get rid of some detainees.

The Bush administration has received a flood of lawsuits from detainees following a Supreme Court decision in June that allowed prisoners to fight their imprisonment, or lodge “habeas corpus” cases in the U.S. federal courts.

“It is just an enormous amount of litigation and the real concern is that one of the habeas judges will order someone released,” said the senior U.S. official.

There is no resolution on what to do with Guantanamo detainees who are neither charged nor returned home.

Matthew Waxman, a former senior Defense and State Department official who dealt with detainee policy, said options included finding a way to prosecute them either via the military commissions or U.S. courts, or just to continue to detain them at Guantanamo.

Another was to send them to a third country, to their own country or to transfer them to the United States.

“But there is certainly a ‘not in my backyard’ problem here. No community is likely to volunteer to be the detention center for these people,” said Waxman.