The delegation represents the Iraqi Accordance Front, which is the biggest Sunni Arab bloc in the Iraqi parliament, occupying 44 seats in the 275 seat parliament.
Adnan al-Dulaimi, the chairman of the Front, said: "There are now around 17,000 Iraqi detainees in Buka camp in the south. Most of them are innocent people. They get arrested and thrown in jail for months and years without charges and without trial, and while in prison they are approached by al-Qaeda people.
"When you are forgotten and suffer psychological pressure you tend to go back to religion and appeal to God to end your ordeal, added to that the desire to take revenge on those who illegally threw you in jail, you tend to be a soft target for extremists."
The delegation held the US army in Iraq responsible for their failure in communicating with armed groups opposed to the US presence in Iraq.
Dhafir al-Ani, a member of the delegation, said: "We have hundreds of examples of people who had nothing to do with armed action, taken to jail, and then released just to join al-Qaeda fighters.
The Front occupies 44 seats out
of Iraq's 275-parliament
"The US army is blindly following tip-offs from Shia sectarians who just want to harm Sunnis for being Sunnis, and the US army is just not getting this and keeps on filling its detention centres with innocent prisoners, most of them under 25 and [who] do not enjoy [a] solid political ideology, which makes them vulnerable and easily influenced by others, mainly al-Qaeda."
Al-Dulaimi criticised US officials for not fulfilling their promises to him personally and to many members of his bloc.
"In every meeting I have with US officials I repeat my appeal to them to take into consideration that they cannot keep people in prison indefinitely without charges.
"It is just not right and gains them nothing but increasing extremists who spend their days in detention looking forward to one thing, which is to be released one day and to take their revenge.
"They keep reassuring me that they would take action but they never did. They release [a] few dozens and the next day arrest hundreds."