Major League Soccer commissioner Don Garber says St. Louis and Sacramento are the leading candidates for the next round of expansion.
Garber said "it's fair to say they're front-runners" at a meeting with the Associated Press Sports Editors on Thursday.
He said other candidates, in order of priority, were Detroit, San Diego, San Antonio, Austin, and Cincinnati.
In a visit to Sacramento last week, Garber confirmed plans to expand the league to 28 teams.
MLS currently has 20 clubs, with Atlanta due to join in 2017 and a second Los Angeles team the following the year.