Aguero sustained a knee injury in City's opening Premier League match against Southampton on Sunday and his club do not expect him back on duty until after the international break. City manager Roberto Mancini has earmarked Aguero for a comeback at Stoke on 15 September.
Argentina play at home against Paraguay on 7 September and then travel to face Peru on 11 September. In a further surprise step, coach Alejandro Sabella has handed a first call-up to 28-year-old Palmeiras striker Hernan Barcos.
Barcos said: "This is a prize after so much effort. It's a proud moment for me to train and compete with great players that I admire."
Argentina squad: Mariano Andujar (Catania), Sergio Romero (Sampdoria); Hugo Campagnaro (Napoli), Federico Fernandez (Napoli), Pablo Zabaleta (Manchester City), Ezequiel Garay (Benfica), Marcos Rojo (Sporting Lisboa), Fabricio Coloccini (Newcastle); Javier Mascherano (Barcelona), Angel Di Maria (Real Madrid), Fernando Gago (Valencia), Enzo Perez (Benfica), Jose Sosa (Metalist), Pablo Guinazu (Internacional); Lionel Messi (Barcelona), Gonzalo Higuain (Real Madrid), Rodrigo Palacio (Internazionale), Sergio Aguero (Manchester City), Ezequiel Lavezzi (Paris St Germain), Hernan Barcos (Palmeiras).