The extra troops will come from the 82nd Airborne Division. "The battalion is being deployed to Iraq. They are going to assist in detention operations," said the spokesman, Lieutenant Colonel Barry Venable on Thursday.
The Washington Post newspaper said the number of prisoners in US-run detention centres in Iraq has doubled in the past 11 months from 5,400 to 10,800.
Venable said the deployment was not linked to "any force level adjustment associated with the elections period" in Iraq.
A referendum is scheduled to be held in October on a new constitution and if it is passed a national election would be held in December.
With the violence claiming a mounting toll, the United States plans to increase its troop levels in Iraq for the elections. There are currently about 138,000 US troops in Iraq.