The Real Madrid forward has been hampered by hamstring and knee complaints ahead of the June 16 clash in Salvador.
"With Ronaldo, I am taking it that he will play but it makes no difference to us," Xinhua quoted Lahm's comments published on FIFA.com.
"He is an exceptional player but we are preparing normally as if he is going to play, as if he will be able to play and we think he will be able to play. For him too, it must be special to face us again, he must be desperate to finally beat us."
Lahm insists Germany are a different side to the one that lost to Spain in the semi-finals of the 2010 World Cup in South Africa.
"There are certain differences between the 2010 World Cup, where lots of players were playing their first major tournament, and (Euro) 2012, where the players were more used to playing at the highest level with their club," Lahm said.
"I believe we still have a very good team now. There are lots of players who are not used to sitting on the bench and not playing from the first minute. That's where team spirit will come into play."