Defense Secretary Ash Carter said Saturday that a U.S. airstrike that is believed to have killed a number of Iraqi soldiers on Friday was a "mistake that involved both sides" and something that "can happen in war."
The airstrike on Friday near Fallujah is the first known instance of friendly fire during Operation Inherent Resolve, the mission targeting ISIS in Iraq and Syria.
Coalition forces were conducting airstrikes in the region with Iraqi forces on the ground, when one of the strikes hit several of the soldiers there, according to a brief statement from the Pentagon.
Military officials said the strikes were done at the request of, and with information, from Iraqi security forces.
"Despite coordination with the Iraqi security forces on the ground, initial reports indicate the possibility one of the strikes resulted in the death of Iraqi soldiers," a statement read.
The statement did not say how many people were killed, but CBS News reported 10 soldiers were killed in the strikes.
The Pentagon said Saturday that Defense Secretary Ash Carter called Iraqi Prime Minister Haider al-Abadi "to express his condolences on the unfortunate loss of Iraqi Security Forces on the front lines of the fight against [ISIS]."
Carter confirmed that both U.S. and Iraqi officials would investigate the incident.
"The secretary and the prime minister committed to work together to prevent such incidents in the future and to ensure that this incident is not exploited by those who wish to create divisions between the United States and Iraq," read a statement from the Pentagon.
Speaking to reporters onboard the USS Kearsarge in the Persian Gulf on Saturday, Carter said the incident was "regrettable."
"These kinds of things happen when you're fighting side by side as we are," he said, describing the airstrike as having "all the indications of being a mistake of the kind that can happen on a dynamic battlefield."
Carter said he and the Iraqi leader recognized that "things like this can happen in war."