The death appears to have occurred during a combat operation, chief of US Central Command Army Gen. Joseph L. Votel aid on Thursday.
The US-led Resolute Support Mission (RSM) in Afghanistan said in a statement that the incident was under investigation.
The identity of the victim was withheld pending the notification of relatives, according to RSM, which is purportedly an “advice and assist mission” consisting of about 14,000 troops, mostly from the US and NATO countries, Presstv reported.
US military authorities said the name of the dead soldier would be released 24 hours after family notification has taken place in keeping with the Pentagon policy.
Taliban militants, meanwhile, claimed on Thursday that they had blown up a US armored vehicle in southern Helmand Province, killing several soldiers on board.
The latest casualty was the eighth so far this year of American troops killed in hostile incidents in Afghanistan. At least seven US troops have been killed in Afghanistan this year in combat incidents or insider attacks by members of the Afghan forces.
Overall, 3,555 US-led troops, including 2,414 American soldiers, have been killed since the US-led war on Afghanistan began in 2001 following the 9/11 terror attacks, according to iCasualties website.
The US invaded Afghanistan in 2001 with the declared aim of toppling the Taliban. The war removed the militant group from power but some 17 years on the Taliban are still active in two-thirds of the country and involved in widespread militancy.
Last year, the United States added thousands of additional troops to its forces in Afghanistan. Washington claims the American troops are deployed in Afghanistan to train its forces and conduct operations against militant groups.