The USA have been handed a tough draw at the World Cup, pitted alongside powerhouse nations Germany, Portugal and Ghana in Group G.
In an interview with the New York Times published on June 4, coach Klinsmann said: "We cannot win this World Cup, because we are not at that level yet."
His comments were met angrily by USA outcast Landon Donovan, who argued the country could lift the trophy if they could beat the likes of Germany.
But speaking ahead of the USA's opening game against Ghana in Natal on Monday, Klinsmann was still sticking to his belief that winning the World Cup was a bridge too far.
"For us now, talking about winning the World Cup is just not realistic," the German told reporters on Wednesday. "First, we have to make it through the group.
"So let's stay with our feet on the ground and say, let's get that group done and then the sky is the limit."
Klinsmann added: "With Greece in 2004, I think nobody from Greece would have said 'We are going to win the European Championship,' but they did.
"The beautiful thing with soccer is it's unpredictable, you don't know what happens."
If the USA are to reach the latter stages of the tournament, they must get off to a winning start against Ghana, who have been described as one of the top African football nations by Klinsmann.
Ghana are a familiar rival, having eliminated the USA after extra time in the round of 16 at the 2010 World Cup in South Africa.
"It's a team full of individual talent with players, certain players that can hurt you within a second if you are not alert and awake," he said.
"That's good that way, I think it's a great way for us to start the tournament.
"I think the guys that were in South Africa in our roster feel like they can correct some things still but obviously we train now for a month very intense and very focused for this opening game.
"We want to get that right starting from the first second, it is a tough team to play there's no doubt about it."
