WASHINGTON (AP) — The Army's top officer warned Friday that it will become increasingly difficult to target and launch precision airstrikes against Islamic State militants hiding among the Iraqi population.

Army Chief of Staff Gen. Ray Odierno told reporters that so far the targets American warplanes and drones have hit in Iraq have largely been out in the open and were "clearly identifiable."

Now, he said, the militant fighters are starting to infiltrate the population, and there are reports that they are using children and others as shields.

"When you target, you want to make sure you are targeting the right people," said Odierno. "The worst thing that can happen for us is if we start killing innocent Iraqis, innocent civilians."

Odierno, a veteran of several years in command in Iraq during the height of the war, knows well how civilian casualties could turn the population against the U.S.-led campaign against the Islamic State group.

He said that in order for the U.S. to maintain the precision of the strikes, Iraqi or other ground troops may be needed to better direct the strikes.

Odierno said the U.S. will determine over time whether any additional ground support is needed. U.S. leaders have ruled out fighting a ground war in Iraq, but they've left the door open for specialized troops to embed with and advise Iraqi units.

U.S. officials will also do routine assessments over time to see if more troops need to be added, Odierno said. Asked if the current total of about 1,600 will be the maximum, he said he thought that number was a good start.

"I don't think there's a rush to have lots of people in there right now," he said, and added that since the fight could go on for several years, adjustments to the numbers would be made if needed.

Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, told senators Tuesday that so far it hasn't been difficult to differentiate between the enemy fighters and the Iraqi security forces or other noncombatants.

"If we get into a circumstance where the forces are very intermingled, then the target discrimination becomes more difficult," Dempsey said, in a response to Sen. Kelly Ayotte, R-N.H. "If we get to the point where I think we need the JTAC (Joint Terminal Air Controller) with the Iraqi security forces, I will make the recommendation. But I'm not there." JTAC refers to troops on the ground who direct the aircraft conducting combat airstrikes and call in target locations.

Dempsey added that there are also new technologies that the military now had that allow troops to have a clearer view of what is happening on the ground.

At the White House on Friday, spokesman Josh Earnest said precautions are being taken to avoid civilian casualties.

"There are measures that are being taken to limit damage or injury to innocent civilians in Iraq and Syria. This is a priority," he said.

___

Associated Press writer Darlene Superville contributed to this report.