Klinsmann was slated in the American media before the FIFA World Cup for saying: "I think for now, talking about winning a World Cup, is just not realistic".
Critics labelled the 49-year-old German coach's comments as "un-American".
But after leading the 13th-ranked Americans out of a difficult group in Brazil that also included Germany, Portugal and Ghana, Klinsmann appeared to have learned from his earlier mistake by talking up his team's chances against world number 11 Belgium on Tuesday.
"We have enough confidence now going into this game – a very special one, a knockout game – to say we are able to beat them," Klinsmann said.
"But we all know we have to go to our extreme and get 100 per cent in each player to make this happen."
Belgium arrived in Brazil with plenty of pundits predicting they could challenge for the title, despite having missed the past two World Cups.
Marc Wilmots' men got through Group H with three tight victories over Algeria, Russia and South Korea but Klinsmann still rates Belgium highly, despite their lack of fluency in the tournament so far.
"(Belgium are one) of the secret favourites in this World Cup because of the players, individual players, that they have," he said.
"We have absolutely no fear at all. We feel like we are in a position now to challenge (them). We believe we have built a foundation in our team that we are able to beat them."
Klinsmann, however, reminded his players they will have to play better than they did in their final Group G match against Germany, which they lost 1-0 on Thursday.
"I was definitely not as happy as with the first two games with the performance they had against Germany," the former striker said.
"Now, going into knockout games, everyone has to call up his 100 per cent for the team.
"I believe that in our team so far, nobody can claim that he reached his 100 per cent yet. This is a very important message to the players, is that now prove it."
