German Chancellor Angela Merkel had dinner with coach Juergen Klinsmann and his World Cup squad on Tuesday and gave her backing to their World Cup campaign.

German chancellor Merkel holds 1974 World Cup trophy during her visit to headquarters of the German Soccer Federation in Frankfurt.[Reuters]

Deputy government spokesman Thomas Steg said Merkel and the entire country were "crossing their fingers" for German success.

She hoped they would open the tournament with a clear victory over Costa Rica in Friday's Group A tie in Munich, Steg said.

Merkel was thanked for her support by German captain Michael Ballack during the two-hour visit to the German team base near the Olympiastadion in Berlin, which hosts the final.

Klinsmann's squad and officials have booked all 54 rooms of the luxury hotel from last Monday until the day after the tournament finishes on July 9.

Merkel's date with the party was organised several weeks ago.