Ange Postecoglou's men are expected to be the easy beats in Group B, which includes Chile, Spain and the Netherlands.
And the Socceroos know the pressure is on their opponents in every group game, starting with Jorge Sampaoli's Chile at the Arena Pantanal in Cuiaba on Friday.
"All of the pressure will be on Chile and we look forward to taking the game to them. Everyone expects them to win," Oar told a news conference on Monday.
"The weight of expectation will be on them. They know if they don't get something their backs will be against the wall.
"So for us, we can go into the game with a lot of confidence and really take it to them.
"We know we’re definitely capable of surprising the opponents (in Group B). If you look at our last game (a 1-0 loss to Croatia), every time we've got better and better."
Oar is wary of Chile's ferocious pressing, with the South Americans having pushed Germany in a 1-0 loss in March.
He said Australia were aiming to get through the press and capitalise on the space left behind.
"We know Chile are very fast and mobile and won't give us time on the ball so we have prepared that way," Oar said.
"We know if they press too much in tight areas and we can find space we can hurt them going forward."
