In an interview with broadcaster ARD, Guttenberg said the Bundeswehr's current structure does match up with operations in eight war zones and hotspots around the world.
Changing the way missions are organised is among the tasks for a new Bundeswehr commission set to take up work on Monday, he said.
Reducing compulsory military service time from nine to six months – a reform that begins October 1 – is just one step forward in the reforms, Guttenberg said.
The defence minister also spoke in favour of constant updates for weapons and equipment, particularly for troops based in Afghanistan.
In response to criticism about inadequate equipment following the death of three soldiers in Kunduz on Good Friday, Guttenberg said that this year Bundeswehr forces there can expect between 150 and 200 new armoured vehicles.
“We must always optimise,” he said. “It's a constant process.”
He also rejected a proposal by incoming parliamentary commissioner for the Bundeswehr Hellmut Königshaus that troops specifically need “Leopard 2” vehicles, saying that Chancellor Angela Merkel had already deemed his suggestion an expression of incompetence.
Last Friday, Merkel and Guttenberg paid their respects to the three soldiers who fell in battle against the Taliban, marking the first time a post-war German leader has attended such a memorial service.