Only about one-fourth of the prisoners held at the Guantanamo naval base are interrogated regularly because there are not enough translators and interrogators to question them all, the U.S. admiral in charge of the detention operation said on Thursday.

In this photo reviewed by US military officials, an unidentified detainee prays inside the compound of Camp Delta detention center, at the Guantanamo Bay U.S. Naval Base, Cuba in this April 6, 2006 file picture. [Reuters]

Rear Adm. Harry Harris, who at the end of March took command of the military task force that runs the camp, said the 460 captives at Guantanamo in Cuba were dangerous men who still provide useful information about al Qaeda tactics, financing and safe houses.

But only those he described as senior al Qaeda and Taliban leaders were routinely questioned by U.S. interrogators, he said.

"It's about around 25 percent of the population that we are actively interrogating," Harris told visiting journalists.

"If we had unlimited interrogators and translators then we could interrogate more. But we have limited resources so we have to focus that the best way we can, so we go after those detainees that have the largest intelligence value."

The rest are not ignored completely, he said. But asked if some prisoners might have gone years without being questioned, he replied, "I would think there are, but I just don't know."

The United States has faced criticism from human rights groups and some of its allies for indefinitely holding prisoners at Guantanamo. President George W. Bush said earlier this month he would like to close the detention center.

Some 759 captives have been held at Guantanamo since the detention operation opened in 2002, and nearly 300 have been released or transferred to their home nations for continued detention, including 15 sent home to Saudi Arabia on Thursday.

Harris said he expected the population to drop further as officials in Washington complete diplomatic negotiations to return about 120 more to their homelands.

He said he was convinced the rest were "truly dangerous men intent on jihad" and must continue to be held for the protection of Americans.

In a far-ranging interview, Harris said the United States will spend $64 million to run the Guantanamo detention operation this year, not counting the $30 million spent on a new medium-security prison that will replace some of the aging cells in August.

He said the Guantanamo captives were well treated and in generally good health, but with the oldest now 71 years old, the military had drafted a plan for dealing with any deaths.

Nearly all the prisoners are Muslim and Harris said a Muslim chaplain was on call and would be sent to Guantanamo to perform traditional rites. He said the body could be returned to the prisoner's homeland or buried at a cemetery on the Guantanamo base but that interment likely would not take place swiftly, as Muslim tradition requires.

"We would conduct an autopsy because we want to understand why the person died," Harris said. "Obviously we're going to be subjected to lots of questions."

Shortly after the interview, a Guantanamo spokesman said two prisoners had attempted suicide on Wednesday by overdosing on prescription medicine they had apparently been hoarding. They received emergency medical treatment, had normal vital signs and were under observation in the camp hospital, said the spokesman, Cmdr. Robert Durand.

He said there had been 39 suicide attempts by 23 Guantanamo prisoners since the camp opened, including 12 attempts by the same man. None have succeeded, Durand said.