At least 15 Afghan forces have been killed when US warplanes conducted an airstrike in Afghanistan's Helmand province.
The US military described the Friday attack as a friendly-fire incident, promising an investigation.
"We would like to express our deepest condolences to the families affected by this unfortunate incident," the US military said in a statement.
It said the airstrike hit a compound in Helmand's Gereshkdistrict, where the Afghan troops had gathered. The Afghan government had already been notified about the air raid, according to the statement.
The statement came short of announcing the number of Afghans who lost their lives in the strike.