Boris Johnson shared a picture of himself with Ukrainian president Volodymyr Zelensky after making a surprise trip to Kyiv.
‘What happens in Ukraine matters to us all,’ the outgoing Prime Minister said on Twitter.
‘That is why I am in Kyiv today. That is why the UK will continue to stand with our Ukrainian friends. I believe Ukraine can and will win this war.’
Today’s visit coincides with the 31st anniversary of Ukraine’s independence from the Soviet Union.
It also comes around six months into Russia’s invasion, with fears Vladimir Putin could unleash a particularly brutal attack to mark the day.
Usually on Independence Day a huge military parade is held in Kyiv city centre, but public events have been banned over concerns the capital could be hit.
During his visit, the PM announced another major package of support including unmanned surveillance and missile systems for the Armed Forces of Ukraine.
The £54 million package of 2,000 state-of-the-art drones and loitering munitions will enable Ukraine to better track and target invading Russian forces.
Mr Johnson added: ‘For the past six months, the United Kingdom has stood shoulder-to-shoulder with Ukraine, supporting this sovereign country to defend itself from this barbaric and illegal invader.
‘Today’s package of support will give the brave and resilient Ukrainian armed forces another boost in capability, allowing them to continue to push back Russian forces and fight for their freedom.’
The package features 850 hand-launched Black Hornet micro-drones – smaller than a mobile phone – which are particularly useful for surveillance in urban warfare.
The Prime Minister will leave office on September 6, the day after either Liz Truss or Rishi Sunak emerges as the victor in the Tory leadership contest.
Mr Johnson has formed a close bond with Mr Zelensky and has made surprise visits to meet him in Kyiv earlier this year.
The PM also received the Order of Liberty, the highest award that can be bestowed on foreign nationals, for the UK’s support for Ukraine.
Britain is also preparing to give mine-hunting vehicles to operate off the coast, with Ukrainian personnel being trained in their use in UK waters in the coming weeks.
Meanwhile, Defence Secretary Ben Wallace said the UK could ‘toughen up’ its visa conditions for Russians, but expressed doubt that a total travel ban was the solution.
Mr Wallace’s comments come as Finland, Estonia and the Czech Republic have called for Brussels to implement an EU-wide ban on new tourist visas for Russians to enter the Schengen free travel area as punishment for Russia’s war against Ukraine.
Mr Zelensky had first urged the visa ban in an interview with the Washington Post earlier this month, saying Russians should ‘live in their own world until they change their philosophy’.
Both the EU and the US have rebuffed Ukraine’s demand so far. Speaking to the BBC Radio 4’s Today programme, Mr Wallace said: ‘I certainly think we can toughen up the conditions of our visas. I am not sure whether an outright ban is the right way.
‘I think that’s a matter for the Home Secretary to look at. But I don’t like, and I’m sure none of your listeners like, watching oligarchs’ wives or indeed Russian senior officials’ wives enjoying themselves in Greece or the south of France, or on super yachts around the world while their army is committing war crimes in Ukraine.’
Despite the war in Ukraine reaching its sixth month and fears the West might be losing interest, the Defence Secretary appeared optimistic.
On the EU’s resolve, Mr Wallace said: ‘I don’t see any waning’ of support. There’s always a few disagreements about the levels of sanctions, but, fundamentally, the international community is united against what Putin is doing.’
Mr Wallace also claimed Russia is in a ‘very fragile position’ at the moment, explaining its advance can be measured ‘in metres per week, not miles’.
On whether Ukraine is realistically in a position to retake the territory that Russia still holds, Mr Wallace said: ‘I think Ukraine is getting itself into that position.’
Ukraine’s ambassador to the UK Vadym Prystaiko marked the occasion by urging UK citizens to be ‘patient’ as the war-torn country ‘cannot afford to lose your support’.
‘You are playing a very important part in this fight. Ukraine will do what it takes to claim victory,’ he said.
Labour leader Sir Keir Starmer paid a visit to Ukrainian and British Army personnel at Salisbury Plain.
He said: ‘My mission, my message to the Ukrainian people, to our troops, our Nato allies, is that on the issue of defending Ukraine against Russian aggression, we stand united.
‘We will not be divided politically in the United Kingdom on this and I’ve been able to deliver that message first-hand amongst this very, very impressive training.’
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