"I can say without exception or equivocation that the United States will not torture," Obama told State Department officials hours after he signed three executive orders and one memorandum that ordered closer of Guantanamo Bay detention centre and CIA secret interrogation centres across the world.

It gave strict instructions that only measures mentioned in the military manual can be applied for interrogation.

"We will immediately undertake a comprehensive review to determine how to hold and try terrorism suspects to best protect our nation and the rule of law," Obama said.

"The world needs to understand that America will be unyielding in its defence of its security and relentless in its pursuit of those who would carry out terrorism or threaten the United States," he asserted.

Referring to the orders he signed earlier, Obama said: "This should send an unmistakable signal that our actions in defence of liberty will be just as our cause and that we, the people, will uphold our fundamental values as vigilantly as we protect our security."

"Once again, America's moral example must be the bedrock and the beacon of our global leadership. With those three executive orders and this memorandum, the message that we are sending around the world is that the US intends to prosecute the ongoing struggle against violence and terrorism."

"We are going to do so vigilantly, we are going to do so effectively, and we are going to do so in a matter that is consistent with our values and our ideals," Obama said.

"The American people understand that we are not, as I said in the inauguration, going to continue with a false choice between our safety and our ideals."

Responding to media queries at his first press briefing, the White House spokesperson, Robert Gibbs said Obama believed that torture is wrong.

"He said that throughout the campaign. And we've taken steps today to make sure that -- that those beliefs are upheld as it relates to detainees and interrogations," Gibbs said.

Earlier in the day, Obama-designated Director National Intelligence, Dennis Blair, said torture is not moral, not legal and not effective. The US government will have a clear and consistent standard for treatment of detainees.

Testifying before the Senate Select Committee on Intelligence, Blair said, "I would say that there would be no water boarding on my watch. There will be no torture on my watch."

UN WELCOMES OBAMA DECISION TO CLOSE DOWN GITMO PRISON

Welcoming the decision of the Obama administration to close detention facility in Guantanamo Bay, the UN has said that there should be accountability for those responsible for the torture of the detainees.

In a statement, UN High Commissioner for Human Rights Navi Pillay demanded compensation for those found innocent and called for a thorough investigation into the allegations of torture at the facility.

"Under international law, there is an absolute prohibition against torture, and other cruel, inhuman and degrading treatment," she said.

"There must be accountability for those who have ordered such practices or carried them out, and victims should receive recompensation"

She appreciated the new administration's decision to ban methods of interrogation which contravene international law and called for a review of the US approach to detaining individuals abroad, in countries such as Afghanistan and Iraq, as well as the practice of "rendition."