Barca are sending a major delegation to the Champions League group draw, with Bartomeu and Messi both due to attend. Messi will attend the ceremony after being nominated for the Best Player in Europe last season.
It will be a rare chance for Bartomeu and Messi to speak face-to-face, reports Sport, after a difficult summer market for the club.
Messi has made it clear via third parties he's unhappy with their work in the transfer window.
It's suggested the pair will also discuss a date for when Messi finally signs the new contract he agreed over a month ago.