Klinsmann's team take on Germany in Recife on Thursday, in a game which will decide their Group G fate.
The Americans were within seconds of securing qualification with a game to spare on Sunday, Silvestre Varela's diving header with practically the last touch of the game earning Portugal a 2-2 draw at the end of an enthralling encounter in Manaus.
As a result, the States need a draw against Klinsmann's compatriots to ensure their progression to the second round, and Klinsmann is hoping for more passionate backing.
"The fans' support for us is overwhelming, it's unbelievable," he told US Soccer's official YouTube channel.
"When we go and take the bus to the stadium and see thousands of US fans streaming towards the stadium chanting it gives us that extra amount of energy that we need.
"We need now all the energy from the fans going to Recife, being loud and pushing for us.
"Seeing the pictures from home, suddenly people are really into soccer and supporting our team and we feel that and get that energy and we'll take that into the game, it helps a lot.
"It makes you feel accountable and responsible for giving everything you have on the field in every World Cup game.
"You have to be in there and take that energy to another lever against Germany."
US Soccer confirmed on Tuesday - via their official Twitter account - that Jozy Altidore would once again miss out, after injuring his hamstring in the win over Ghana, but defender Matt Besler will be available after suffering a similar problem.
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