Human Rights Watch said U.S. military authorities were holding 513 Iraqi children as of May 12 as "imperative threats to security".
Since the March 2003 U.S.-led invasion, the United States has detained 2,400 children under the age of 18 in Iraq, including some as young as 10, it said.
Child detainees were sometimes interrogated over days or weeks by military units in the field before being sent to main detention centres and had no real opportunity to challenge their detention, the human rights group said.
"The vast majority of children detained in Iraq languish for months in U.S. military custody," said Clarisa Bencomo, a researcher for Human Rights Watch.
The US military response:
Responding to Human Rights Watch, a U.S. military spokesman said U.S. forces currently held fewer than 500 children in Iraq.
Youths charged under Iraqi law received access to legal counsel. "Those who are not referred to the Iraqi criminal courts do not have legal counsel because they are not charged with a crime," said Major Matthew Morgan, a spokesman for U.S. detention facilities in Iraq.
Military representatives defend the practice of detaining children, saying that Iraqi militants use them to attack government and coalition forces. The tragedy is that children are the most vulnerable and exploited foot soldiers in many of the world’s most prolonged wars and conflicts. The war in Iraq is no exception, and US soldiers are confronting the fact that their mission to "spread democracy to the Middle East" means taking young children from their families and interrogating them. And for what? Some meager shred of intelligence that would clear the fog of the Iraq war?
We need a new strategy in Iraq, one that doesn’t involve throwing kids in jail. There is no military solution to Iraq’s political problems, and we need to bring the troops home. Waiting for the next president to make it all better isn’t good enough.