Insurgent attacks in Baghdad have risen despite a recent security crackdown in which thousands of troops were deployed and new checkpoints were mounted.
"I think since we have started Operation Together Forward, you'll find that the number of attacks are going up," US army Col Jeffrey Snow told reporters on a videoconference from Baghdad.
He said informing locals about the new security measures assisted insurgents informed of the military's plans.
Col Snow could not provide statistics but said he was not surprised at the increase in attacks.
"As we populated and put additional patrols, both dismounted and mounted, into neighborhoods ... and we increased the number of checkpoints, we expected that there would be an increase in the number of attacks.
"I believe that these attacks are going to go down over time. So I remain optimistic," he said.
Baghdad remains one of the more dangerous areas of Iraq. Its residents are subject to dusk-to-dawn curfews but lawlessness has not diminished.
Meanwhile the US military has launched a criminal investigation into soldiers who allegedly killed a family of four Iraqi civilians in their home south of Baghdad.
A preliminary military inquiry into the incident found sufficient reason to move to a formal criminal investigation, the military said in a statement released in Baghdad.
It is the latest in a series of investigations in which US troops are suspected in the killings of civilians.