LANGLEY, Virginia – President Barack Obama heaped praise on the CIA, vowing his "full support" and telling employees not to be discouraged by his release of stunning details on the agency's harsh terror interrogations.

The president got an enthusiastic reception as he gave a speech at the agency's headquarters, just days after releasing secret memos on Bush-era questioning of terror suspects derided by critics as torture.

"Don't be discouraged by what's happened the last few weeks. Don't be discouraged that we have to acknowledge potentially we have made some mistakes -- that's how we learn," Obama said.

"But the fact that we are willing to acknowledge them and then move forward, that is precisely why I am proud to be president of the United States and that's why you should be proud to be members of the CIA."

Obama's visit coincided with fresh revelations about the repeated use of waterboarding, or near drowning, on up to 266 occasions by CIA interrogators against two top Al-Qaeda terror suspects.

Last week, the president released a series of Justice Department memos detailing harsh techniques, including waterboarding, sleep deprivation and even a proposal to use insects, endorsed by the previous administration of George W. Bush.

The move, in line with a court order, exposed Obama to fierce attacks from across the political spectrum.

Former Bush administration officials warned he had tied the hands of the agency for the future, damaged individual agents who carried out the questioning or offered a propaganda tool to US enemies.

Human rights groups were furious that Obama simultaneously ruled out prosecutions of CIA operatives who carried out interrogations viewed as torture, by reasoning that they were acting on orders to defend their country.

Obama, however, vowed "my full support" for the Central Intelligence Agency, calling it "an indispensable tool, the tip of the spear, in America's intelligence mission and our national security."

"I need everybody to be clear: We will protect your identities and your security as you vigorously pursue your missions. I will be as vigorous in protecting you, as you are vigorous in protecting the American people," he said.

Before his remarks, Obama met privately with 50 intelligence officers and agency leaders and acknowledged later that "people have expressed understandable anxiety and concern."

"I'm sure that sometimes it seems as if ... we're operating with one hand tied behind our back, or that those who would argue for a higher standard are naive. I understand that.

"What makes the United States special and what makes you special is precisely the fact that we are willing to uphold our values and our ideals even when it's hard, not just when it's easy; even when we are afraid and under threat, not just when it's expedient to do so."

If there were hard feelings at CIA, they were not on public display.

Nearly 1,000 CIA employees packed the lobby of the agency's original headquarters building to hear Obama. When he strode in, accompanied by CIA director Leon Panetta, they exploded in cheers and applause, jumping to their feet and waving their arms.

"I've got an Amen corner out here," Obama quipped at one point.

The euphoric reception was in sharp contrast with what was reported to have been an intense behind the scenes debate over whether to release the interrogation memos, which Panetta and other CIA officials argued against.

Former CIA chief Michael Hayden warned on Sunday that the release of the documents could still leave agents vulnerable to civil lawsuits or congressional probes targeting CIA operatives who relied on the Bush-era memos to carry out harsh interrogations.

"There will be more revelations. There will be more commissions. There will be more investigations," he told the TV program "Fox News Sunday."

This is an agency, he added, "that is at war and is on the frontlines of defending America."

The harsh interrogation techniques, Hayden insisted, had succeeded in combating Al-Qaeda and saving American lives, something he characterized as "an inconvenient truth."

Obama showered praise on the agency operatives who operate in the shadows and have played a new and more vital role since the September 11 attacks in 2001.

"I want you to know how much the American people appreciate your service," Obama said.