Europe must step up urgently to improve its defence and make Nato 'more European to maintain its strength', because the US has shaken the transatlantic relationship to its foundation, the EU's foreign policy chief has warned.

The US would continue to be Europe's partner and ally, Kaja Kallas told a defence conference, but no great power had ever 'outsourced its survival and survived'.

Tensions with the US flared when President Donald Trump threatened to take over Greenland, a semi-autonomous Danish territory.

Kallas's remarks came after Nato leader Mark Rutte prompted a backlash when he said European lawmakers should 'keep on dreaming' if they thought Europe could defend itself without the US.

French Foreign Minister Jean-Noël Barrot reacted by stating, 'No, dear Mark Rutte. Europeans can and must take control of their security. Even the United States agrees. It's the European pillar of Nato.'

Kaja Kallas said that under the Trump administration Europe was 'no longer Washington's primary centre of gravity', and the continent needed to change the culture away from thinking as nations, towards acting jointly as Europeans.

Washington's transition away from Europe has been ongoing for a while, Kallas noted, adding that it was structural, not temporary.

The 23 nations that were members of both the EU and Nato had a special responsibility to 'sync our efforts, together with Nato'.

Addressing the same conference, EU Defence Commissioner Andrius Kubilius emphasized the need for an independent European defence strategy without delays and excuses.