Germany said borders must not be changed by force after US President-elect Donald Trump refused to rule out military action to take control of Greenland.
The vast Arctic island is an autonomous territory of EU and Nato member Denmark.
German government spokesman Steffen Hebestreit said that "as always, the firm principle applies... that borders must not be moved by force," highlighting international agreements such as the UN Charter.
Hebestreit refused to be drawn on whether Berlin took Trump's threats against Denmark seriously.
"I don't want to assess" the comments, Hebestreit told a regular news conference, adding simply that the German government had "taken note" of them.
French Foreign Minister Jean-Noel Barrot also demanded that Trump should not threaten the European Union's "sovereign borders."
"There is no question of the EU letting other nations in the world, whoever they may be, attack its sovereign borders," Foreign Minister Jean-Noel Barrot told France Inter radio.
He added that, while he did not believe the US "would invade" Greenland, "we have entered an era that is seeing the return of the law of the strongest."
"There is obviously no question that the European Union would let other nations of the world attack its sovereign borders, whoever they are," Barrot said. "We are a strong continent."
The EU described Trump's Greenland remarks as "wild hypothetical stuff."
"We are talking about fairly wild hypothetical stuff about an administration that hasn't come in yet," a European Commission spokesperson said, according to AFP news agency. The same spokesperson said the EU is looking forward to working with the Trump administration.
