Cardinal Edmund Szoka led the Archdiocese of Detroit before holding top administrative jobs in Rome.
The 85-year-old pope said Monday he's stepping down because of declining strength.
Szoka said Catholics should pray that the pope has "more years of quiet life and that the cardinals will select a worthy successor."
Cardinal Adam Maida succeeded Szoka as Detroit's archbishop and participated in the 2005 papal selection. Maida said it's a sad moment, but hopes the pope experiences "the peace and joy of Christ as he begins a new chapter of his life."