The bombing killed 22 people.
Army General John Campbell told a congressional committee in Washington that Afghan forces requested the airstrike. The Afghan forces said Taliban fighters were firing from the hospital.
The hospital is operated by the international medical charity Doctors Without Borders, or Médecins Sans Frontières in French.
General Campbell said the U.S. led the raid after reviewing the request.
"To be clear, the decision to provide aerial fire was a U.S. decision made within the U.S. chain of command," Campbell said. "A hospital was mistakenly struck. We would never intentionally target a protected medical facility."
General Campbell did not discuss additional details about the airstrike. U.S. and Afghan investigations into the bombing continue.
At the White House, spokesman Josh Earnest called the bombing a "profound tragedy and something the United States takes very seriously."
The attack killed 12 workers and 10 patients of Doctors Without Borders.
The president of Doctors Without Borders, Joanne Liu, said that the attack "cannot be brushed aside as a mere mistake or an inevitable consequence of war."
Words in This Story
charity - n. an organization that helps people who are poor, sick, etc.
intentionally - adv. done in a way that is planned
profound - adj. very strongly felt
brush aside (phrasal verb) - to refuse to consider something seriously because you feel it is not important