Washington, D.C.-based Americans United for Separation of Church and State first sent a letter to the city in July, seeking the removal of the cross from Cross Park. A response is expected by the end of this week.
The organization said the cross in the park across from Bronner's Christmas Wonderland violates the U.S. Constitution.
The Frankenmuth Parks and Recreation website states the white cross "is a tribute to the religious background of the Frankenmuth community."
Frankenmuth, about 75 miles northwest of Detroit, is represented by the Ann Arbor-based Thomas More Law Center.