According to Syrian state-run television, a 33-year-old Michigan woman, Nicole Lynn Mansfield, was shot dead by government forces. She was part of an al-Qaeda influenced group.
Mansfield was shot while driving in Idlib and aired her license in which she is seen to wear an Islamic headscarf and her address listed as Flint, Michigan.
The FBI agents also confirmed the news after Syrian state television broadcast images of her passport on Wednesday.
Earlier, the State Department said the US authorities were aware of the case and were working with the Czech Republic mission in Syria to get more information.
The woman was reported to be traveling with two other unidentified Westerners, both British citizens, when forces loyal to President Bashar al-Assad opened fire.
Syrian state television said the three deceased individuals were fighting with al-Qaeda affiliated rebels and were carrying weapons when they opened fire.
Other images shown on Syrian state television include a cache of weapons the three were carrying, a hand drawn map of a government military facility and a flag belonging to the al-Qaeda affiliated al-Nusra Front.
This will not be the first time that American agents have been killed while fighting in Syria's civil war.
In March, Eric Harroun, 30, a former soldier from Phoenix was also arrested and returned to the United States from Syria.
He was charged with using a rocket-propelled grenade during his time in Syria where he fought for terrorist group of al-Nusra Front.