(Reuters) - Group G heavyweights Germany and Portugal will trade blows in the blazing midday heat of Salvador on Monday with goal machine Cristiano Ronaldo fit to take on the three-time World Cup winners.
Portugal talisman Ronaldo's participation had been in doubt after struggling with tendinosis in his left knee.
Germany, second in FIFA's world rankings behind Spain, will be at full strength after several key players, including keeper Manuel Neuer and captain Philipp Lahm, recovered from injuries.
In the other Group G match, the United States will try to gain a measure of revenge against Ghana in Natal after the Africans knocked them out of the last two World Cups.
Outsiders Iran take on African champions Nigeria in Curitiba, hoping to cause a surprise in their opening Group F fixture.
(Reporting by Erik Kirschbaum; editing by Justin Palmer; firstname.lastname@example.org, Reuters messaging: email@example.com)