Foreign Secretary Ed Miliband has acknowledged that Donald Trump's deal to import Russian diesel has strained diplomatic relations with Ukraine's allies, including the UK.
Speaking at the Warsaw Security Forum, Mr Miliband said it had been a "very difficult few days" in relations with Washington following the US president's announcement.
Support for Zelensky
Mr Miliband and European allies gave a public show of support to Ukraine's Volodymyr Zelensky after Mr Trump suggested Ukraine needs a new leader and claimed Russian President Vladimir Putin wanted a peace deal more than the Kyiv government.
Mr Miliband said Mr Zelensky had shown "extraordinary leadership over the last four-and-a-half years in the most difficult of circumstances" since Mr Putin's invasion.
He added: "I was with him in Ukraine last week as we went to the site where 22 innocent civilians were killed, including five children. He feels every death personally and I think we should praise his leadership today from this forum."
Energy ceasefire call
The Foreign Secretary said the issue of an "energy ceasefire" raised by Mr Trump should be taken seriously "because in the last week alone we've seen 200 Russian attacks on Ukrainian energy infrastructure".
He added: "So let us take up this idea of the full energy ceasefire and let us seek with President Trump to hold Putin to this full energy ceasefire, because that is what we need. And President Zelensky has shown his openness to this idea."
Mr Miliband said the UK would act with the European Union if the bloc could agree measures to use frozen Russian assets to support Ukraine.
He added: "We know that every wrong message that is sent to President Putin is a message that sets back our security and sets back the Ukrainian cause, and we need to send the right messages."
Hybrid warfare warning
Mr Miliband also said Europe had to do more to respond to Russia's hybrid warfare threat, calling it "a new form of confrontation".
He said: "Our resolve is being tested as far as Ukraine is concerned, and our resolve is being tested with Russian hybrid warfare."
He added that whether it is disinformation, misinformation, espionage or cyber attacks, "all of these things across Europe, we have to take it much, much more seriously and look at all the tools at our disposal to counter it".
Mr Zelensky said Russia's bombardment of his country's cities and energy infrastructure had continued overnight but Ukraine "received no early warning from our partners" about a ballistic missile strike on Kyiv.
He said: "Intelligence on Russian ballistic missile launches helps save lives, and this is one of the most critical issues. This is precisely what helps prevent people from being killed – when there is an early warning about ballistic missiles."
He said Russia had also continued to hit Ukraine's energy infrastructure, adding: "Ukraine has not carried out strikes on Russian oil refineries or the energy sector in general for the two days since the American president announced an energy ceasefire. But Russia did not heed the American president. During this time, the Russians have attacked both our energy facilities and our critical infrastructure, sending absolutely clear signals that they have no intention of refraining from strikes on Ukraine."
He added that "direct or indirect support for Russia, slowing down assistance to Ukraine and making it harder to protect lives against ballistic missiles will certainly not help bring peace".
The US president claimed Mr Putin wanted a peace deal more than Ukraine's leader, and insisted both men "have to get together and end that ridiculous war".
His barb at Mr Zelensky followed a renewed spat between the pair after the US president announced the controversial diesel deal with Russia in a bid to bring down soaring domestic fuel costs ahead of critical stateside elections next month, which will decide control of Congress.
Speaking as he left the White House to travel to a campaign rally in Ohio on Monday, Mr Trump said: "All I know is that Zelensky and Putin have to get together and end that ridiculous war."
He added: "I think they want to make a deal, but they don't know how. But we're going to get them to make a deal. I think actually Putin wants to make a deal more than Zelensky."
The US president also insisted an energy ceasefire was already in place between Ukraine and Russia, saying: "Well, they agreed. Because I said, 'You agree.' That's why they agreed, because I said they agree."
When pressed about the attacks by Russia, Mr Trump said: "Well, I'd have to look at it and see, because there's been violations on both sides."
