"A service member with Combined Joint Task Force - Operation Inherent Resolve died in Syria, 21 July. Initial reports indicate the incident was not due to enemy contact. The incident is under investigation," the statement said.
The military did not disclose the name and service branch of the deceased serviceman.
The US-led coalition of over 60 nations has been carrying out airstrikes and other operations against the Daesh* terror group in Iraq since August 2014 and in Syria since September 2014.
However, the coalition has acted in Syria without the approval of the Syrian government or the UN Security Council.
*Daesh (also known as ISIS, IS) is a terrorist organization banned in Russia