"What Donald Trump is proposing is unrealistic. We will not end up with 5%," Habeck told the Funke media group.
The Greens minister called for increasing defense spending to 3.5% of GDP, stressing that the increase would be temporary.
"3.5% is roughly what is currently being discussed in NATO as a medium-term goal... If we ensure a reasonable level of security for Germany in a few years we will be able to reduce spending again," Habeck said.