Pulisic was substituted at half-time of the USA's opening 4-1 win against Paraguay a week ago after suffering a calf injury and has not fully recovered.
"Christian is not available," Pochettino told Fox Sports.
"His evolution is (going) really well, yesterday he was training.
"I hope that as soon as possible he can be ready to be selected again to be part of the team."
The USA and Australia can qualify for the knockout rounds with a victory in their Group D game in Seattle.