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, BBC reported. 

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, according to BBC.