Trump, who meets Russian President Vladimir Putin in Finland on Monday, this week accused Germany of being a "captive" of Russia due to its energy reliance, before a NATO summit where he pressed allies to more than double defense spending.
On Thursday, Trump described Putin as a "competitor" rather than an "enemy" and said he expected they would get on well when they hold their first summit in Helsinki. Trump also said the meeting with Putin may be the easiest on his Europe trip.
Maas welcomed the meeting, at which the US president has said he will raise the issue of nuclear weapons reduction, Reuters reported.
"We have always said that we need dialogue with Russia. That's why it's good if Washington and Moscow talk to each other," Maas told the Bild am Sonntag newspaper. "It would be a step forward if this meeting also provided impetus for nuclear disarmament."
But Maas added: "He who offends his partners, risks losing in the end. Unilateral deals at the expense of one's own partners also harm the US in the end."