In its annual survey of human rights around the world, the New York-based group dubbed the abuse of prisoners by US forces in Iraq one of the most flagrant examples of violations in 2004 that needed special attention.
HRW singled out the prison abuse because of the US' visible posture in the world on questions of international rights and civil justice.
"The US government is less and less able to push for justice abroad because it's unable to see justice done at home," said the group's director, Kenneth Roth, who said recent US action on the "war on terror" had compromised Washington's authority on human rights and civil justice matters.
"Governments facing human rights pressure from the United States now find it easy to turn the tables," Roth said at a Washington press conference announcing publication of the report. "Washington can't very well uphold principles that it violates itself."
Practise what's preached
Particularly in the case of Abu Ghraib, as well as US-run facilities at Guantanamo Bay, Cuba, and in Afghanistan, "when a superpower flouts these kinds of basic standards, it erodes the standard", he said.
The accused ringleader of the abuse at Abu Ghraib is now facing a court martial in the US. Specialist Charles Graner has said he was following orders to soften up prisoners for interrogation. The US military has insisted abuse was not condoned.
But Roth said that while the US now insists that it does not encourage the use of torture, Washington is still willing to countenance the use of "cruel, inhumane or degrading treatment" that stops just short of it.
He found particularly insidious Washington's use of detainee "disappearances", in which foreign terror suspects are held at US-run facilities overseas with no record of their presence.
"When a person is disappeared, he is extremely vulnerable to torture," said Roth.
He said a special investigator would be less vulnerable to political pressure than recent internal US government probes, and would be less likely to limit its prosecution to "a handful of privates and sergeants".
"The most senior officials should be subject to the laws of the land," he said.
Human Rights Watch is also calling for the establishment of a special commission, modelled after the September 11 commission that probed the causes and possible fixes to security lapses that led to the massive attacks on New York and Washington in 2001, to investigate the prison abuse scandals.
HRW also highlighted the atrocities in Sudan, where the United Nations estimates about 70,000 people have died in recent months and about 1.5 million displaced.
Roth called for criminal prosecutions there, too.
"The crimes of Darfur must not go unpunished," he said, adding that "the International Criminal Court would be the most efficient and effective institution to prosecute these crimes".
The HRW report lamented that "the systematic violence against civilians by Sudanese government forces and government-backed militia constitutes crimes against humanity, and has even been described by some as genocide.
"Yet," the report continued, "the international response has been little more than to condemn the atrocities, feed the victims and send a handful of poorly equipped African forces to try, largely in vain, to stop the slaughter".