The UK prime minister joined French President Emmanuel Macron, German Chancellor Friedrich Merz and Polish Prime Minister Donald Tusk for the meeting, which was hosted by Ukrainian Prime Minister Volodymyr Zelensky.
Other members of the “coalition of the willing” participated remotely, including Italy’s Prime Minister Giorgia Meloni, Canadian PM Mark Carney, President of the European Commission Ursula von der Leyen, and Mark Rutte, the secretary-general of Nato.
In a phone call with Donald Trump following the meeting, the US president reportedly reaffirmed his support for the ceasefire, after Vladimir Putin rejected his initial proposal in March.
Sir Keir said Trump was “absolutely clear that this is a demand that must be met”.
The leaders assembled in Kyiv warned that “new and massive” sanctions will be imposed on Russia’s energy and banking sectors if Putin does not agree to the unconditional 30-day ceasefire “in the air, at sea and on land”.
Sir Keir told the BBC that “material progress” had been made during the meeting.
“We’ve been able to collectively get to a much better position and a more unified position today that holds out a better prospect of a ceasefire,” he said.
“You’ve got unity in the demand, but also unity in what the response will be if the demand is not met. We haven’t seen that sort of unity during this conflict.”
“I’m not going to pretend this is the end of the process but this is a significant moment we now need to push on and make sure this happens,” he added.
Further coordinating sanctions on Russian oil, fossil fuels and other assets would make a “material difference”, the prime minister said.
The Kremlin reacted to the proposal by accusing European leaders of making “contradictory” and “generally confrontational” remarks about Russia.
Press secretary Dmitry Peskov said that Ukraine’s allies must stop sending weapons to Ukraine before any ceasefire can happen – something European leaders have rejected – before later saying Russia would consider the proposal.
“We have to think about this. This is a new development,” state-run Russian news agency Tass reported Peskov as saying.
