The NATO-led Resolute Support mission said in a brief statement that the individual died during combat operations in Afghanistan on Thursday.
The service member’s identity is being withheld until their family is notified.
It brings the number of US troops killed in Afghanistan to at least 15 in 2019.
This latest death came during ongoing talks between a US envoy and the Taliban, which are aimed at ending 18 years of military intervention.
The United States invaded Afghanistan in 2001 after the September 11 attacks.
Taliban spokesman Suhail Shaheen, said last week a deal could be expected “as soon as the remaining points are finalised”.
Washington wants to withdraw thousands of US troops from Afghanistan, but only on the condition that the Taliban renounces its connections to al-Qaeda and pledges a ceasefire.
The conflict in Afghanistan continues to have a devastating impact on civilians in the country, and the latest UN figures document more than 3,000 casualties in the first half of 2019.