Mohammad Vakili’s boys beat their South American rivals 3-1 (25-27,25-21, 25-17,25-13) in Pool B.
Titleholder Iran will face Italy on Sunday.
Iran defeated Bulgaria 3-1 in its first match but lost to the Czech Republic on Friday.
The 2019 FIVB Volleyball Boys' U-19 World Championship is the sixteenth edition of the FIVB Volleyball Boys' U-19 World Championship, contested by the men's national teams under the age of 19 of the members of the Fédération Internationale de Volleyball (FIVB), the sport's global governing body.
The tournament is being held in Tunisia from August 21 to 30.