"There is no pact of non-aggression, that isn't going to happen," Bravo said ahead of Tuesday's much-awaited tie in Sao Paulo. "They aren't going to gift us anything, it's their last game."
Chile lie third in the 10-team South American group and anything less than a win in Brazil means automatic qualification for Russia will depend on the results of Tuesday's four other matches.
The top four teams qualify automatically and the fifth-placed team take on New Zealand in an intercontinental playoff.
Five-times world champions Brazil are already through and second-placed Uruguay are almost certain to join them. But only two points separate the next five teams, with Argentina, finalists in 2014, sixth and out of the qualification places.
Chile are the Copa America champions but have performed poorly in the qualifiers this year, losing two in a row before recovering to beat Ecuador 2-1 on Thursday.
Bravo said that win had bolstered their confidence and he expressed optimism ahead of the trip to Brazil, a team they have never beaten away from home.
"We recovered a bit of our essence in the last match and that will boost us," goalkeeper Bravo told reporters. "We have the players and the team to hurt Brazil."
Chile will be without midfield dynamo Arturo Vidal, who will miss the game through suspension.
(Reporting by Felipe Iturrieta, Writing by Andrew Downie, Editing by Rex Gowar)
