U.S. NAVAL BASE, Guantanamo Bay, Cuba (Reuters) - In the small, bare rooms where foreign terrorism suspects are interrogated at the U.S. Guantanamo Bay military prison, swivel chairs and cups of tea can be useful tools, the senior interrogator said.

The treatment of the 600 prisoners at Guantanamo has come under scrutiny since the abuse of prisoners in Iraq by U.S. troops was revealed in April, when pictures emerged of bound prisoners being sexually humiliated and threatened by dogs.

The military has acknowledged that the techniques were used in Iraq after recommendations from the former Guantanamo prison chief on ways to get more information from detainees.

Some released Guantanamo prisoners have said they were shackled in "stress" positions for hours while they were questioned and that threatening dogs, strobe lights, freezing air and other methods were used.

But officials who spoke with reporters visiting the prison this week portrayed the exchanges at Guantanamo more as a battle of wits than a confrontation.

They denied reports of ill-treatment and said that unlike Abu Ghraib prison in Iraq, Guantanamo was tightly controlled and the military police were highly trained.

Brig. Gen. Jay Hood, commander of the task force that runs the prison operation, said the prisoners were treated in compliance with the Geneva Conventions and that the camp was run in a "safe, secure and humane" manner.

The camp's senior interrogator, a Marine and Navy veteran who is a homicide detective in civilian life and who spoke on condition he not be identified, portrayed his work as a subtle psychological battle to get prisoners to tell what they might know about terrorist plans.

"It's a mental chess game," he said. "About 99 percent of what we do down here is not even close to the general definition of interrogation - confrontational, adversarial and hostile." Hostility doesn't work, he said.

"You wake somebody up in the middle of the night, bring him into the booth and he's not going to be very happy. Unhappy people don't cooperate," he said.

EMOTIONAL NERVE

Interrogations take place in rooms with closed-circuit cameras or two-way mirrors that allow an analyst to watch. The analyst cross-checks a database for links to information provided by others and suggests lines of questioning.

A psychiatrist advises the team, watching for cues as to which questions hit an emotional nerve.

Prisoners are brought in shackled at the legs and arms, and each interrogation room has a metal ring in the floor for securing the shackles. Removing the chains is a gesture aimed at instilling trust.

The chairs swivel and the interrogator's chair is very deliberately a bit higher than the prisoner's, so the detainee has to look up at him.

"Everything in this room is a tool," the interrogator said. He wheels his chair closer to encourage a cooperative prisoner and swivels it away to show skepticism.

"Nobody likes to be called a liar, even when they're lying," the interrogator said. "You just back up a little bit, wheel away from them."

Building rapport can mean sharing a Big Mac meal from the base McDonalds or chatting about soccer and children. One of the best interrogators is a small Arabic-speaking woman who brings thermos flasks of tea to put her subjects at ease.

Most of the prisoners were captured during the U.S.-led war to oust al Qaeda and their Taliban protectors from Afghanistan. Many know each other from training camps or have tribal ties, and some have opened up after becoming convinced their colleagues squealed on them, the interrogator said.

"Once they start to realize that we're learning things, they often want to correct it, minimize what they've done," he said. "If they're proud of what they've done, we get them to talk about it."

One prisoner pointed to the acoustic tiles on the wall and bragged that he could make a bomb by grinding the tiles and mixing them with common chemicals. Others proudly sketched drawings of explosives detonators they were trained to use, the interrogator said. Some have identified members or leaders of terrorist sleeper cells, he said.

Prisoners are questioned as often as every three or four weeks, but drawing them out is a long, slow process, he said.