US Secretary of State Marco Rubio sought to reassure a nervous Europe on Saturday, saying Washington wanted to recharge the transatlantic alliance so a strong Europe could help the United States on its mission of global "renewal".

Speaking at a security conference in Munich after months of turmoil in US-European relations sparked by President Donald Trump's vows to seize Greenland and his often derisive remarks about allies, Washington's top diplomat struck a markedly soothing tone.

"We do not seek to separate, but to revitalise an old friendship and renew the greatest civilisation in human history," Rubio said, calling for "a reinvigorated alliance".

"We want Europe to be strong," Rubio said, adding that the continent and the United States "belong together."

He echoed the Trump administration's oft-stated assertion that immigration poses a threat, saying that "mass migration" is "a crisis which is transforming and destabilising societies all across the West".

He said Europe and the United States were "heirs to the same great and noble civilisation" and that he hoped Europe "together with us are willing and able to defend it".

Aside from immigration, Rubio otherwise largely avoided the Maga flashpoint and culture-war issues that German Chancellor Friedrich Merz said on Friday had deepened a "rift" between US and Europe.

Rubio's speech marked a sharp contrast to that of US Vice President JD Vance a year ago, when he used the same stage to attack European policies on a range of issues including free speech and immigration.

The Trump administration has also charged that Europe faces a "civilisational decline", and has courted far-right parties on the continent.

Ties plunged last month when Trump stepped up threats to annex Greenland, an autonomous territory of Nato member Denmark, forcing European nations to stand firm in protest.

Some breathed a sigh of relief after Rubio's speech, with Estonia's Defence Minister Hanno Pevkur saying: "It was needed to show that we are still allies and partners."

But others ⁠struck a more cautious tone.

"I am not sure ⁠that Europeans see the announced civilisational decline, supposedly caused mainly by migration and deindustrialisation, as a core uniting interest. For most Europeans, the common interest is security," said Gabrielius Landsbergis, former foreign minister of Nato member Lithuania.

"This was not a departure from the general position of the (Trump) administration. It was simply delivered in more polite terms," he said ⁠on X.

European leaders at the Munich Security Conference have pledged to shoulder more of the burden of shared Nato defences, saying this was essential for Europe to counter a hostile Russia.

European Commission chief Ursula von der Leyen told the gathering that "Europe needs to step up and has to take on its responsibility" for its security, including closer ties with Britain 10 years after Brexit.

British Prime Minsiter Keir Starmer echoed the sentiment, saying: "We must build our hard power, because that is the currency of the age," and calling to build "a shared industrial base across Europe which can turbocharge our defence production".

Nato Secretary-General Mark Rutte told reporters that although France and Britain, Europe's only nuclear powers, have discussed greater cooperation to make their nuclear deterrence stronger, "nobody is arguing in Europe to do this as a sort of replacement of the nuclear umbrella of the United States." (Agencies)