Barack Obama apologized to Doctors Without Borders International President Joanne Liu during a phone call Wednesday morning, following a deadly strike on one of the group’s medical facilities in Afghanistan.

Obama “assured Dr. Liu that the Department of Defense investigation currently underway would provide a transparent, thorough and objective accounting of the facts and circumstances of the incident, and that if necessary, the president would implement changes that would make tragedies like this one less likely to occur in the future,” White House spokesman Josh Earnest said.

“There was a mistake, and it’s one that the United States owns up to,” he added.

The medical aid group has called for an independent international investigation into the Saturday attack in the northern Afghan city of Kunduz that killed 22 people, including 12 of its staff.

The White House had previously stopped short of issuing a full apology for what a senior U.S. general acknowledged earlier this week was a “mistake”.

But Earnest said that based on what Obama learned “he believed it was appropriate for the United States to do what we’ve done before, which is to acknowledge that a mistake had been made, to offer an apology, to do so in a transparent way, to own up to our mistakes and to vow to carry out a full investigation to get to the bottom of what had happened”.

There are three investigations currently underway, including those conducted by the Pentagon, NATO and Afghan government.

Obama pledged a “transparent, thorough and objective investigation” to Liu during their call, according to Earnest. The White House spokesman did not address the aid group’s demand for an independent investigation, instead emphasizing the reliability of the Pentagon’s investigation.

If that inquiry indicates that the U.S.’s military rules of engagement require change, “that’s what the President will expect the Department of Defense to do,“ Earnest said.

Doctors Without Borders has described what transpired over the weekend as a possible war crime, but Earnest said “there’s no evidence that I’ve seen or that anybody else has presented that indicates that this was anything other than a terrible, tragic mistake”.

He further urged patience while the U.S. conducts its internal probe, and said that the “conduct of the individuals involved will be under investigation”.

At the State Department, spokesman John Kirby, a former Pentagon spokesman, addressed concerns about the military’s ability to conduct an independent investigation. “The reason why the military is so good at investigating itself is because it does pull into investigations agencies or units outside the one involved,” he said.

“That’s what gives it the independence,” he added.

Obama also spoke with his Afghan counterpart, Ashraf Ghani, to convey his condolences and “noted that he looked forward to continuing to work closely with President Ghani and the Afghan government to support their efforts to provide security for the Afghan people,” Earnest said (Anadolu Agency).

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