Neymar scored twice to give Brazil a 2-1 lead over Cameroon at halftime of their last Group A match on Monday.
Neymar scored on either side of Cameroon's goal in the 26th. He opened the scoring off a low cross by midfielder Luiz Gustavo in the 17th minute, deftly side-footing the ball into the net from close range, then restored the lead with a low right-foot strike from the top of the penalty area in the 35th after a pass by left back Marcelo.
Midfielder Joel Matip had equalized for Cameroon with a tap-in from inside the area after a cross by Allan Nyom.
Brazil needs at least a draw to advance to the second round, and a win should be enough to secure first place in the group. Mexico and Croatia were playing the other group match.