Messi has not played for club side Inter Miami since suffering an ankle injury in Argentina's 1-0 victory over Colombia in the Copa America final.
Roma forward Dybala has not made an international appearance since March 2023 but could get an opportunity to add to his 38 caps in Messi's absence.
The reigning world champions will also be without Angel Di Maria after the veteran winger's international retirement.
Argentina are currently top of South American qualifying for the 2026 tournament in the United States, Canada and Mexico.
The top six teams in the 10-nation table will qualify automatically for the finals.
Scaloni's men will host Chile on September 6, before facing Colombia in Barranquilla four days later.
Squad
Goalkeepers: Emiliano Martinez (Aston Villa/ENG), Juan Musso (Atalanta/ITA), Geronimo Rulli (Marseille/FRA), Walter Benitez (PSV Eindhoven/NED)
Defenders: Gonzalo Montiel (Sevilla/ESP), Nahuel Molina (Atletico Madrid/ESP), Leonardo Balerdi (Marseille/FRA), Cristian Romero (Tottenham/ENG), German Pezzella (River Plate), Nicolas Otamendi (Benfica/POR), Lisandro Martinez (Manchester United/ENG), Nicolas Tagliafico (Lyon/FRA), Valentin Barco (Sevilla/ESP).
Midfielders: Guido Rodriguez (West Ham/ENG), Leandro Paredes (Roma/ITA), Alexis Mac Allister (Liverpool/ENG), Rodrigo De Paul (Atletico Madrid/ESP), Ezequiel Fernandez (Al Qadsiah/KSA), Enzo Fernandez (Chelsea/ENG), Giovani Lo Celso (Tottenham/ENG)
Forwards: Alejandro Garnacho (Manchester United/ENG), Nicolas Gonzalez (Fiorentina/ITA), Lautaro Martinez (Inter Milan/ITA), Valentin Carboni (Monza/ITA) Julian Alvarez (Atletico Madrid/ESP), Giuliano Simeone (Atletico Madrid/ESP), Valentin Castellanos (Lazio/ITA), Matias Soule (Roma/ITA), Paulo Dybala (Roma/ITA)
