The United States said Wednesday it did not condone torture under any circumstances, but acknowledged to a UN anti-torture watchdog it had "crossed the line" following the September 11 attacks.
"The US is proud of its record as a leader in respecting, promoting and defending human rights and the rule of law, both at home and around the world," acting US legal advisor Mary McLeod told the 10-member UN Committee on Torture.
"But in the wake of 9/11 attacks, we regrettably did not always live up to our own values," she said.
"We crossed the line and we take responsibility for that," she said, quoting US President Barack Obama.
McLeod was one of about 30 top US officials gathered in Geneva for Washington's first grilling by the committee since 2006.
In its first review since Obama came to power, several delegates acknowledged abuses had occurred during the so-called "War on Terror" under the previous administration of George W. Bush.
"We recognise that no nation is perfect, ours included," Keith Harper, US ambassador to the UN Human Rights Council, told the committee.
The delegation faced a barrage of questions from committee members on how the country was dealing with rectifying and providing redress for acknowledged abuses during the "war on terror".
The US delegation was asked to explain why the US military prison at Guantanamo Bay in Cuba remains open, why many detainees remain there without charge and when Washington plans to shut it down.
The committee members also questioned the treatment of prisoners there, and lack of redress for victims of the widely publicised abuses by US troops at the Abu Ghraib prison in Iraq in the early 2000s.
Beyond the "war on terror" legacy, the committee members raised issues of abuses in US prisons, rape in prisons, the broad use of drawn-out solitary confinement, and long years on death row.
And they asked how Washington could justify its widespread detention of non-violent, non-criminal illegal immigrants, including minors.
And they slammed police brutality that appears to disproportionately affect minorities, such as 18-year-old Michael Brown, who was shot and killed by white police officer Darren Wilson in Ferguson, Missouri last August.
His parents were in Geneva this week to take part in events on the sidelines of the committee hearing.
The committee is set to publish its conclusions on November 28.