Reporter Manuel Veth followed with transfer talks between the sides.
Mihailovic is currently one of the 14 players under contract with the Fire.
The 21-year-old Homegrown midfielder is coming off his most productive season with the Fire, scoring three goals and adding a pair of assists in 27 appearances, including 16 starts. Mihailovic has made five appearances with the US men’s national team, scoring his first goal against Panama after being called into Gregg Berhalter’s January camp. He figures to be a prominent player for the U-23 side as the US looks to qualify for the 2020 Olympics.