NATO says a U.S. soldier has died as a result of injuries sustained during a "vehicle incident" in eastern Afghanistan.
Two other U.S. service members were injured in the December 11 incident in Nangarhar Province, the NATO Resolute Support mission in Afghanistan said.
It added that the incident was "not the result of enemy action."
The Western-backed government in Kabul has struggled to fend off the Taliban and other militants since the withdrawal of most NATO troops in 2014.
Under its new strategy for Afghanistan, the administration of U.S. President Donald Trump has committed 3,000 additional troops to the country, on top of the 11,000 already there, to train and assist Afghan security forces in their battle against the militants.