Coalition vows to build up further against Islamic State

Other U.S. officials, speaking on condition of anonymity to discuss details not yet publicly released, said that Keating, 31, and his SEAL advisory team were moving between Kurdish Peshmerga units when they got caught in a firefight with Islamic State forces that had created a breach in Peshmerga lines.

Carter and his counterparts from 11 coalition countries met behind closed doors at the headquarters of U.S. European Command, where Carter was presiding at a change-of-command ceremony Tuesday when news of Keating's death reached him.

The Peshmerga are Kurdish militia who have generally fought more effectively against the Islamic State in northern Iraq than the regular Iraqi security forces.

The U.S. has been training, equipping and advising Pershmerga forces as well as Iraqi security forces, and the Pentagon recently pledged up to $415 million in aid to the Kurds.

Carter expressed condolences Keating's death, which is the third U.S. combat death in Iraq since U.S. forces returned there in mid-2014 to help the Iraqi government regain the wide swaths of territory captured by the Islamic State.