Ms Truss and Mr Kuleba said it was “imperative that the G7 and Nato this week demonstrate that their commitment to Ukraine will never be surpassed by Putin’s determination to seize it”.
“That means increasing and speeding up their supply of heavy weapons, continuing to sanction all those colluding in Putin’s war, and cutting off imports of Russian energy completely,” they added.
Although other world leaders have also visited Mr Zelensky in Kyiv, Mr Johnson has sought to portray Britain as Ukraine’s closest ally.
“The UK, US and other European leaders all want to see the same thing – a democratic, sovereign and thriving Ukraine that is able to defend itself against further aggression,” the Prime Minister's official spokesman said on Saturday.
“The PM visited Kyiv last week for discussions with President Zelensky, who made clear that Ukraine has no interest in surrendering sovereignty.”
The UK is also pledging to guarantee another £429 million in World Bank loans to Ukraine, amid concerns its government could collapse by the autumn without further support.
The pledge brings Britain’s total commitment to £1.5bn, including £1.3bn in loan guarantees and £220m in direct humanitarian aid.
This week will see world leaders converge first on Munich for the G7 summit, then on Madrid for a full conference of Nato members.
Representatives for Finland and Sweden are also expected to join a meeting to discuss their accession to Nato.
Leaders will discuss the war in Ukraine’s impact on the global economy, food security and the future of Western alliances.
Ahead of the summits, Mr Johnson said: “Future generations will be awed and inspired by the truly heroic Ukrainian resistance in the face of Putin’s barbarism.
“Ukraine can win and it will win. But they need our backing to do so. Now is not the time to give up on Ukraine.
“The UK will continue to back Ukraine every step of the way, because we know that their security is our security, and their freedom is our freedom.”
