WASHINGTON — The United States military has made progress in its effort to identify moderate Syrian rebels to train for the fight against Islamic State militants and a U.S. training mission could begin this spring, the Pentagon said on Tuesday.

Rear Adm. John Kirby, the Pentagon press secretary, welcomed statements from Ankara indicating Turkey and the U.S. plan to conclude a deal this month on training and equipping moderate Syrian rebels, part of a U.S.-led campaign to counter Islamic State forces in Iraq and Syria.

Kirby said Maj. Gen. Michael Nagata, commander of U.S. special operations forces in the Middle East, was in the process of talking with Syrian opposition groups in an effort to identify individual recruits to train and equip.

“I think if we continue to make the progress that we’re making now, that we believe that we could start conducting some training of moderate opposition by early spring,” Kirby told a news conference.

The U.S. began conducting air strikes against Islamic State militants in Iraq and Syria last year after the group overran part of northwestern Iraq and Baghdad asked for Washington’s assistance.

President Barack Obama has authorized more than 3,000 U.S. troops to advise and assist Iraqi forces and to train 12 brigades of Iraqi troops, including three from the Kurdish peshmerga forces.

He also approved a mission for the U.S. military to train and equip a moderate force of Syrian rebels to counter Islamic State militants active in Syria, which is in the midst of a civil war between President Bashar al-Assad and his opponents.

The Pentagon hopes to be able to train about 5,000 moderate Syrian rebels a year for three years. Turkey, Saudi Arabia and Qatar have agreed to host training sites for the rebels, but Kirby did not specify where the training might start.

Kirby said air strikes by a U.S.-led coalition, as well as movements on the ground by Iraqi and Kurdish forces had blunted the momentum of Islamic State.

Asked about casualties in the campaign, the Pentagon spokesman said the Defense Department believed several hundred militants had been killed, but he said he it did not have the ability to track all of those killed and killing was not the goal.

“The goal is to degrade and destroy their capabilities. We’re not getting into an issue of body counts,” he said.

He said the military was actively investigating several incidents where U.S. attacks may have caused civilian casualties but was not able to provide specifics. Military officials in the past generally have rejected claims of civilian casualties.