Donald Trump has said he would love to have Russia return to the G7 group of advanced economies, and that expelling the country "was a mistake".
Russia had been a member of the club of industrialised nations, then known as the G8, until it was excluded following its annexation of Ukraine's Crimea region in 2014.
"I'd love to have them back. I think it was a mistake to throw them out. Look, it's not a question of liking Russia or not liking Russia," the US president said at the White House.
He also said that "high-level people from Russia" will attend the Munich Security Conference on Friday.
"Russia is going to be there with our people. Ukraine is also invited," the president added.
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During a series of fast-paced announcements, including a series of US trade tariffs, he also said he wants to discuss reducing defence spending with Russia and China, halve domestic defence expenditure and support moves towards getting rid of nuclear weapons.
The US president had already announced on Wednesday that he and Vladimir Putin would start peace talks "immediately" to end the war in Ukraine.
But much of Thursday's focus on global defence and spending came after a fractious NATO meeting in Brussels.
It has been an intense 24 hours of diplomacy in Brussels, during which:
• Ukraine's president said his country must have a place at the negotiating table.
• The Kremlin's spokesman Dmitri Peskov said Ukraine would be involved in peace talks "one way or another".
• Donald Trump's defence secretary Pete Hegseth reiterated the US vow to focus its military might away from Europe - telling NATO allies: "Trump won't allow anyone to turn Uncle Sam into Uncle Sucker."
'Make NATO great again'
Mr Hegseth told NATO allies that the US will not guarantee Europe's security and pressured leaders to spend more on their militaries.
He told reporters "we must make NATO great again" as he called on allies to do "far more for Europe's defence".
In terms of military spending, as a proportion of a country's GDP, the US defence secretary said: "2% is a start... but it's not enough. Nor is 3%, nor is 4% - more like 5% - real investment, real urgency."
Sky News' US correspondent Mark Stone, who was listening to Mr Hegseth's comments, said "he represents one man, Donald Trump, and he speaks for him".
Stone points out that, whether people will like him or loathe him, he "is not a man who has experience in the forum he now finds himself in".
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'Ukraine is just the first stage'
In response to the Trump administration's shift in policy, a European defence minister warned the continent will see its "darkest times since the Second World War" as Russia seeks to rearm and regroup following any peace deal.
Dovile Sakaliene, Lithuania's defence minister, told reporters: "China and Russia are going to coordinate their actions and if we are not able to work together as a team for the democratic world, it is going to be the darkest times since the Second World War.
"In a few years, we will be in a situation where Russia - with the speed that it's developing its defence industry and its army - is going to move forward."
"We all understand that Ukraine is just the first stage currently of an imperial expansion of Russia."
She added that NATO partners have a stark choice - rebuild their armed forces and defence industries "swiftly and very significantly" or find themselves "in a very difficult situation to put it diplomatically".
Senior politicians in Moscow crowed over the thawing of relations between Russia and the US after presidents Trump and Putin held a 90-minute phone call on Wednesday.
Dmitry Medvedev, a former president and current security official, mocked Europe's role on the world stage and said the continent is "mad with jealousy and rage" and that "Europe's time is over".
(c) Sky News 2025: Donald Trump calls for Russia to return to G7 - as European defence minister