Washington (CNN) President Barack Obama called and apologized to the head of Doctors Without Borders, whose staff and patients were killed and injured during a bombing Saturday in Kunduz, Afghanistan, the White House said Wednesday.

The U.S. has characterized its airstrike Saturday, which killed 12 members of the Doctors Without Borders staff as well as 10 patients, as a mistake.

Obama pledged full cooperation with the joint investigations being conducted with NATO and the Afghan government in the morning conversation with Doctor's Without Borders International President Joanne Liu.

"The President assured Dr. Liu that the Department of Defense investigation currently under way would provide a transparent, thorough and objective accounting of the facts and circumstances of the incident and, if necessary, the President would implement changes that would make tragedies like this one less likely to occur in the future," White House Press Secretary Josh Earnest told reporters.

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