The US says it will not hand over detainees to the Iraqi authorities until they raise levels of care.
Iraqi security forces have faced repeated allegations of abuse
After the discovery of hundreds of neglected prisoners held by Iraq's interior ministry, an official said Iraq still had to meet US standards.
"We will not pass on facilities or detainees until they meet the standards we define and that we are using today," Major General John Gardner said.
He added the US had "come a long way" since the Abu Ghraib scandal.
"Abu Ghraib was criminal and I was appalled," Gen Gardner, head of US military prisons in Iraq, told the New York Times.
The huge prison complex became infamous after photographs revealed the abuse and sexual humiliation of detainees by US guards.
The US military admitted that most US-run prisons in Iraq are severely overcrowded, and that its target of handing over facilities and detainees to the local authorities next year could be set back, the newspaper said.
"A specific timeline for doing this is difficult to project at this stage with so many variables," US military spokesman Lieutenant Colonel Barry Johnson said.
"The transition will be based on meeting standards, not on a timeline."
The US says there are more than 14,000 prisoners held in US custody - up from about 8,000 in January - and more than 3,000 had still not come before a court.
US Ambassador to Iraq Zalmay Khalilzad said this month that at least 120 abused prisoners had been found in two detention facilities run by Iraq's interior ministry.
The alleged abuse discovered by US and Iraqi troops included electric shocks and the removal of finger nails.
Sunni groups in Iraq have claimed that torture is common in Shia-run prisons.