Amid growing calls for his sacking, under-fire United States head coach Jurgen Klinsmann remains defiant, insisting his critics "don't understand soccer or the team".

Klinsmann's job is under extreme pressure after USA suffered a humiliating 4-0 defeat to Costa Rica in CONCACAF World Cup qualifying.

It was the nation's worst defeat in a World Cup qualifier since 1957 as USA dropped to the bottom of the Hexagonal phase, having lost 2-1 to rivals Mexico four days earlier.

But Klinsmann, who has been at the helm since 2011, said he does not fear losing his job, warning US Soccer president Sunil Gulati not to make an emotional decision.

"I'm not afraid," Klinsmann told the New York Times. "What you need to do is stick to the facts.

"Soccer is emotional and a lot of people make conclusions without knowing anything about the inside of the team or the sport. I still believe we will get the points we need to qualify, and I am even confident we could win the group.

"The fact is, we lost two games. There is a lot of talk from people who don't understand soccer or the team."

Klinsmann added: "We are coaching a team through a transitional phase.

"We still have to break in younger players. We still have to look for leadership for the team. There are still a lot of technical and chemistry challenges ahead that are normal in this time period. And you put the final pieces together as you go towards Russia, which I am absolutely sure we will do."

"I always made it clear to Sunil, if you really want to move up to the top 15 in the world, you need to have consistency in what you're doing. If you react emotionally, you will become a rollercoaster," he continued.