"Their confidence is going to be high."
Germany convincingly defeated the USA 4-2 in a friendly earlier this year - but Voeller is adamant this counts for nothing when compared to a World Cup fixture.
"That was a friendly this will be
different," said the coach.
"We know that we will have to play better than we did in the second round against Paraguay if want to get to the semi-finals."
Goalkeeper Oliver Kahn is also keen to play down the significance of March's friendly encounter.
"The win might give us a tiny psychological advantage, but this
is the World Cup," said Kahn.
"The Americans are a strong side, with big, strong
"But we're in good shape and the atmosphere within the squad is good.
"We've got to be extremely careful not to be knocked out like we were in 1994 and 1998," he said, referring to Germany's quarter-final exits at the last two World Cups.
Voeller hits back
Meanwhile, Voeller has said that he is tired of the criticism his team have received following their lacklustre display in narrowly overcoming Paraguay in the second round.
"I was the first to say that we didn't play that well but
some of the things that have been said were a bit over the
top," said Voeller.
"There are many teams here who have not played better than we have. We have nothing to be ashamed of."
"What has been written, in particular in the international
press, was not always fair.
"The expectations we had coming here and the fact that we had three players suspended should have taken into consideration."