Based mostly on statements by senior administration officials in 2005, the human rights group said the reassurances of President George Bush that the United States does not torture suspects were deceptive and rang hollow.
"In 2005 it became disturbingly clear that the abuse of detainees had become a deliberate, central part of the Bush administration's strategy of interrogating terrorist suspects," the report said.
Bush's repeated assurances that US interrogators do not torture prisoners deceptively and studiously avoid mentioning that international law prohibits cruel, inhuman or degrading treatment of prisoners, Human Rights Watch said.
In fact, last January, Alberto Gonzales, the attorney-general, claimed in Senate testimony the power to use cruel, inhuman or degrading treatment as long as the prisoner was not an American and was held outside the US, the report said.
"Other governments obviously subject detainees to such treatment or worse, but they do so clandestinely," the report said.
Human Rights Watch says US
policy is fuelling terrorism
"The Bush administration is the only government in the world known to claim this power openly, as a matter of official policy, and to pretend that it is lawful."
The White House has flatly rejected Human Rights Watch's criticisms, saying the group was undermining itself by pursuing "a political agenda".
"I'm rejecting the description of the United States," spokesman Scott McClellan said, admiting that he was had not seen the actual report, only media coverage of it.
"When a group like this makes some of these assertions, it
diminishes the effectiveness of that organisation," he said. "It
appears to be based more on a political agenda than facts."
In recent years, Human Rights Watch has emphasised its conviction that abuses in the name of fighting terror are unjustified and counterproductive.
Kenneth Roth, executive director of the group, said he remained worried over Bush assertion that he retained "commander in chief authority" to order abusive interrogations.
The report accuses Bush of
seeking to justify torture
The report said that last March Porter Goss, the CIA director, justified a torture technique called water-boarding, in which the victim is made to believe that he is about to drown.
In addition the report noted that in Senate testimony last August Timothy Flanigan, a former deputy White House counsel, said the administration would not rule out the use of mock executions in interrogation situations.
It went on to add that evidence shows abusive interrogation has been a conscious policy choice by senior US government officials and cannot be reduced to the misdeeds of a few low-ranking soldiers.
Roth said the tactics were fuelling terrorist recruitment,
discouraging public assistance against counterterrorists
and making prosecution of many detainees impossible.
"The hypocrisy factor has encouraged copycat techniques
around the world by people who do like the United States does," said Roth, adding that the policies of the current administration had "weakened the United States as one of the traditional important supporters of human rights".
The report was was also highly critical of some US allies.
It criticized Britain for trying to send terrorism suspects to countries where they faced torture and said Canada had tried
to dilute a new treaty outlawing enforced disappearances.
It said those practices by US allies - combined with the European Union's practice of subordinating human rights to trade in its relationships with many rights offenders - left a "global leadership void" in defending human rights.
"Sadly, Russia and China were all too happy to fill that void by building economic, political, and military alliances without regard to the human rights practices of their partners." the report said.
"In 2005 it became disturbingly clear that the abuse of detainees had become a deliberate, central part of the Bush administration's strategy of interrogating terrorist suspects"
Human Rights Watch
Russia, trying to counter democratic currents in former Soviet states, and China, seeking resources for its economy,
bolstered abusive governments, creating pressure for other
powers to do the same or risk losing influence, it said.
Among several "bright spots" on the global human rights scene, the report said increased international pressure on Myanmar, formerly known as Burma, and North Korea were among optimistic signs.
The group also lauded India for freezing military aid to Nepal
after a royal coup there in February and credited Kyrgyzstan
for rescuing more than 400 refugees from a massacre in its
Central Asian neighbour, Uzbekistan.