More than 1900 athletes from 192 teams will be in action at Eugene’s Hayward Field between 15-24 July.
Discus thrower Hadadi will have a difficult task in the competition since the best throwers of the world will compete in the event.
Pirjahan, who was forced to miss the 2020 Olympic Games after testing positive for COVID-19, will represent Iran at the 400 meters event.