US Attorney General Alberto Gonzales has discussed legal and security issues with Iraq's deputy PM in Baghdad.
Gonzales determined US policy on the treatment of Iraqi prisoners
Mr Gonzales, who has played a leading role in drawing up US policy on the treatment of prisoners, discussed the question of torture with Barham Saleh.
On the question of how Iraqi forces should treat suspected insurgents, Mr Gonzales said "it is difficult to decide what is appropriate".
Mr Gonzales also stressed the importance of the rule of law in Iraq.
The attorney general said the US was against any kind of torture:
"This president has been very clear. This government has not engaged in torture."
But he also said it was "a difficult decision as to where to draw the line" on how Iraqi police should treat captives in their struggle to stem the violence in Iraq.
"This decision will be made by the Iraqi government," he said.
He also met officials at the Iraqi High Tribunal, which is trying ex-leader Saddam Hussein and six others on charges of war crimes and crimes against humanity.
Mr Gonzales had a crucial role in drawing up guidelines on the treatment of detainees captured during the "war on terror" - defending a robust policy for the interrogation of terrorist suspects.
As such, critics blamed him for giving the green light for violent treatment, which they say led to the abuse scandal at Abu Ghraib prison in Iraq.