They face Ghana in their final group match in Brasilia next Thursday needing to win and hoping that the result in Germany's meeting with the USA goes in their favour.
"The result is not good," Bento told reporters. "A 2-2 doesn't put us out immediately, but it does leave us in a difficult situation. Our chances aren't good.
"Even if it goes down to goal difference, USA have a positive score and we are on minus four.
"The 2-2 result was down to our efforts throughout the match. Our opponents only ever really threatened from distance, but we did have difficulties down the right wing and were unable to control them."
Portugal were knocked out in the last 16 of the World Cup four years ago in South Africa by Iberian rivals Spain.