European leaders have voiced their objection after US President Donald Trump again raised the prospect of annexing Greenland, amid mounting alarm over Washington's actions abroad.

Trump reiterated his territorial ambitions on Sunday, telling European allies, "We do need Greenland, absolutely."

Greenland's Prime Minister Jens-Frederik Nielsen dismissed the idea of US control over the island as a "fantasy", while Denmark's Prime Minister Mette Frederiksen said annexation would make "absolutely no sense".

They were supported by Finland's President Alexander Stubb, who wrote on X: "No one decides for Greenland and Denmark but Greenland and Denmark themselves. Our Nordic friend Denmark and (Frederiksen) have our full support."

Frederiksen said on Monday that a US takeover of Greenland would amount to the end of NATO.

Germany's Foreign Minister Johann Wadephul said: "Greenland is part of the Kingdom of Denmark. And since Denmark is a member of NATO, Greenland will, in principle, also be subject to NATO defense."

The European Union's foreign policy chief, Kaja Kallas, emphasized the principles of international law and the UN Charter. "Members of the UN Security Council have a particular responsibility to uphold those principles, as a pillar of the international security architecture," she said on X.

Jian Junbo, director of the Center for China-Europe Relations at Fudan University in Shanghai, said: "Apparently, Trump is pushing for US hegemony in the Western Hemisphere in a revival of the Monroe Doctrine or any other excuse. Facing such a giant, it's never a waste to take better care of territories."