Lahm gave Germany a sixth minute lead against Costa Rica

"We're working hard," said Klinsmann. "The team played to a high tempo. There are always going to be mistakes and opponents will always get chances."

Klinsmann reserved special praise for Philipp Lahm, who put Germany ahead and Miroslav Klose, who netted twice.

"It was great what Philipp Lahm did and Miro had a very strong performance."

Klinsmann added: "We can feel an incredible energy.

"We're happy to get three points in the opening match.

"Sure, there was some tension. We wanted to get through it without any yellow cards and we wanted to give the crowd something to cheer about."

Left-back Lahm also paid tribute to Germany's fans.

"It is always important to start off with a win," said the Bayern Munich defender Lahm, who scored with a superb shot in the sixth minute.

"You could see what euphoria there was in the stadium.

"Part of the victory should be credited to the fans. They were the 12th man on the pitch."

Meanwhile Klinsmann defended his decision to leave out captain Michael Ballack, who claimed he was fit to play.

Klinsmann said: "The decision to leave out Ballack was a normal one for the coach.

"He said he was ready and could definitely play but we had a scan and saw some injury on his leg.

"We will never take a risk. We will build him up slowly and surely.

"It is not a problem if a player says he wants to play. It was the opening match - very special. Doctors have been working on him and he is raring to go.

"But we had to tell him we were responsible for the whole team. We would have been devoid of responsibility if we had let him play.