German Foreign Minister Johann Wadephul said on Monday that Greenland belonged to Denmark and that the NATO alliance could discuss strengthening its protection if necessary.

Wadephul was speaking after US President Donald Trump made renewed threats to take over Greenland, a prospect that alarmed NATO allies and has taken on a new urgency after Trump followed through on threats to topple Venezuelan leader Nicolas Maduro.

Trump has repeatedly said he wants to take over Greenland, an ambition first voiced in 2019 during his first presidency.

On Sunday, he told The Atlantic magazine in an interview: "We do need Greenland, absolutely. We need it for defence."

Speaking to reporters in Lithuania, Wadephul said Germany had questions about Maduro's removal and stressed the Venezuelan people should determine their country's future in free and fair elections, after Trump said the US would run the country.

On Greenland, Wadephul stressed it was part of Denmark.

"And since Denmark is a member of NATO, Greenland will, in principle, also be subject to NATO defence," he said.

"And if there are further requirements to strengthen defence efforts concerning Greenland, then we will have to discuss this within the framework of the alliance."

He did not elaborate on the nature of those discussions.