US Secretary of State Marco Rubio has spoken of a defining moment and a "new era" as he travels to Europe to give a major speech at the Munich Security Conference,
BBC reports.
Rubio will lead the US team at the first major global event since President Donald Trump threatened Denmark's sovereignty with a pledge to annex Greenland.
French President Emmanuel Macron has insisted Europe must prepare for independence from the US, while Nato Secretary General Mark Rutte stressed that transatlantic bonds were as close and important as ever.
The war in Ukraine, tensions with China and a potential nuclear deal between Iran and the US are also on the agenda at the annual security conference, which began on Friday.
"The world is changing very fast right in front of us," Rubio told reporters, when asked if his message to Europeans would be more conciliatory than a year ago.
"We live in a new era in geopolitics, and it's going to require all of us to sort of re-examine what that looks like and what our role is going to be."
At last year's conference, US Vice-President JD Vance attacked Europe, including the UK, for policies on free speech and immigration. His comments triggered a year of unprecedented transatlantic tension.
Opening this year's conference, German Chancellor Friedrich Merz appealed directly to the US, saying "let's repair and revive transatlantic trust together".
He also revealed that "confidential talks" were ongoing with Macron on creating a joint European nuclear deterrent.
France and the UK are the only two nuclear powers in Europe - but Germany and many other European nations have traditionally relied on the US nuclear umbrella within the Nato alliance for deterrence.
Some 50 world leaders are set to attend this year's event, where European defence and the future of the transatlantic relationship will be discussed at a time when US commitments to Nato have been called into question.
Tensions have been heightened in recent months as Trump has repeatedly said that Greenland is vital to US national security, stating without evidence that it was "covered with Russian and Chinese ships all over the place".
Danish Prime Minister Mette Frederiksen said on Friday she planned to meet Rubio to discuss the US threats to seize Greenland - Denmark's semi-autonomous territory from its Nato ally.
The US threats have been viewed by many European leaders as a watershed moment that has eroded trust with its biggest ally.
Ahead of the conference, eight former US ambassadors to Nato and eight former American supreme commanders in Europe issued an open letter calling for Washington to maintain its support for the Western defensive alliance.
