The committee was also shown US military memos saying that the techniques should be curbed while international monitors were present.
The hearing is the committee's first attempt to discover the origins of the harsh interrogation methods used in Guantanamo Bay prison in Cuba and Abu Ghraib in Iraq and how policy decisions on interrogations were agreed across the US department of defence.
The CIA has admitted it used waterboarding, which simulates drowning, on several suspected al-Qaeda leaders, while US soldiers were photographed using dogs against prisoners at Abu Ghraib.
The interrogations have been widely condemned by international human rights groups.
Lindsey Graham, a Republican senator, said the Bush administration's legal analysis on detainees and interrogations following the September 11, 2001, attacks would "go down in history as some of the most irresponsible and shortsighted legal analysis ever provided to our nation's military and intelligence communities".
The Pentagon's most senior civilian lawyer at the time, William Haynes, was expected to testify at the hearing.
Also present were Richard Shiffrin, Haynes' former deputy on intelligence issues, as well as the legal advisers at the time to the chairman of the Joint Chiefs of Staff and the Guantanamo Bay prison.
According to the senate committee's findings, Haynes became interested in the use of harsher interrogation methods as early as July 2002 when his office inquired into a military programme that trained soldiers on how to resist enemy interrogations.
|Protesters have campaigned against the|
use of waterboarding [Reuters]
Haynes and other officials wanted to know if the programme - known as Survival Evasion Resistance and Escape (SERE) training - could be used used to develop more effective interrogation methods, the committee said.
Shiffrin said his interest in the programme was mainly to use military expertise in interrogations.
However, the head of the Joint Personnel Recovery Agency, which ran the SERE programme, told the committee that the programme included resistance to sensory deprivation, sleep disruption, stress positions, waterboarding and slapping.
The committee further released previously secret memos dating from 2002, when the programme of harsh interrogations began at Guantanamo Bay.
In one of them, the most senior military lawyer at Guantanamo, Lieutenant-Colonel Diane Beaver, says the US defence department had hidden prisoners who were being treated harshly, or abusively, from the International Committee of the Red Cross (ICRC), which monitors the treatment of military prisoners.
Beaver also said the military was secretly using previously forbidden techniques, such as sleep deprivation, but hiding them so as not to draw "negative attention", according to minutes of the committee meeting.
"Officially it is not happening," Beaver said, according to minutes from the meeting.
|The treatment of detainees in Guantanamo has|
caused global controversy [GALLO/GETTY]
"The ICRC is a serious concern. They will be in and out, scrutinising our operations, unless they are displeased and decide to protest and leave.
"This would draw a lot of negative attention."
Beaver said interrogators should "curb the harsher operations while ICRC is around".
Beaver was speaking at an October 2, 2002, meeting between CIA and military lawyers and military intelligence officials on how to break down the resistance of Guantanamo detainees to interrogations.
A senior CIA lawyer at the meeting, John Fredman, said that whether harsh interrogation amount to torture "is a matter of perception".
"If the detainee dies you're doing it wrong," Fredman said, according to a memo.
Beaver also wrote in a memo dated October 11, 2002, that abusive methods could be used against detainees at Guantanamo Bay prison because they were not considered prisoners of war.
Her proposed methods included extended isolation, 20-hour interrogations, death threats and waterboarding.
On Tuesday, Beaver told the committee that she was surprised her memo justifying harsh interrogation techniques was the sole opinion relied on by the Pentagon.
"I did not expect that my opinion ... would become the final word," she said.