Speaking at the headquarters of Deutsche Boerse Group, which operates the Frankfurt Stock Exchange, Merz called on Europe to become more independent of its traditional ally and argued that old certainties no longer held.

"We must become more sovereign and independent, especially in terms of technology," Merz said. "And yes, this also applies to the United States of America".

Suggestions by US President Donald Trump that his country could annex Greenland, an autonomous territory of European NATO ally Denmark, have rocked European leaders.

French President Emmanuel Macron called the episode "a strategic wake-up call for all of Europe" and EU energy commissioner Dan Jorgensen warned the bloc risked becoming dependant on imports of US liquefied natural gas.

Merz said Europe had to adjust to "a new part of the reality we are confronted with".

"Transatlantic relations have changed," he said. "No one in this room says this with more regret than I do, but nostalgia and memories of good times gone by do not help."