Sweden's former prime minister Carl Bildt has accused Russia of working with the US to undermine Ukraine's position.
"I think what the Russians are doing at the moment, apart from watching in sort of pure disbelief … is that they are increasing both the political and military pressure on Ukraine," he told 7.30.
"They do that to a certain extent in cooperation with the US in order to get the weakening of the Ukrainian position prior to the critical meetings."
Mr Bildt, who is also co-chair of the European Council on Foreign Relations, told 7.30 European leaders and the Trump administration were now pursuing opposing strategies to end the war in Ukraine.
"The key thing — and here is the divide across the Atlantic — is that Europeans are convinced that the only way forward is to increase support for Ukraine and strengthen pressure on Putin, while the Trump team seems to be believing that they could ease up and be nice to the Russians and increase pressure on Ukraine."
Mr Bildt says transatlantic relations have never been worse after US President Donald Trump accused Ukraine's President Volodymyr Zelensky of being disrespectful to America and "gambling with World War III."
"We are certainly in the worst moment of the transatlantic alliance … for a generation," Mr Bildt told 7.30.
"We've never seen anything like that, because it's a meltdown on the relationship, on an issue that is fundamental to the security of Europe.
"There have been crises before … where Europe was divided, but here we have all of Europe virtually on the same side and being aghast at what we see happening in the White House."
European leaders standing by Ukraine
British Prime Minister Keir Starmer convened European leaders plus Canada's Prime Minister Justin Trudeau to London to discuss ways to restart negotiations. The UK and France have proposed a temporary truce "in the air and at sea".
Mr Bildt said supporting Ukraine in defending itself against Russia's aggression was the priority.
"It's a very long front line. It will require strong defence by Ukraine, and the Ukrainian army has shown that it's very capable," he said. "But it requires money."
Mr Bildt said like-minded countries, including Australia, should continue to support Ukraine.
"What I hope will come out of the continuation of the London meeting is as a broad coalition of the willing, of European and other countries — Canadians, hopefully Australians, Japanese and others — who are prepared to give that support to Ukraine, so that Ukraine, after some sort of ceasefire, will be able to defend itself," he said.
Asked whether the Trump administration's behaviour offered any clues as to how it would respond to a change in the status quo in Taiwan, Mr Bildt said there was no clear answer.
"What we would like to have is a really reliable and responsible American global power," he said.
"We don't have a reliable, responsible American power at the moment.
"That introduces an element of uncertainty in our security calculations. It could turn out OK, it could turn out disastrously, but we simply don't know.
"It is a profoundly unpredictable United States that we have to deal with at the moment."
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