Boris Johnson has announced that the UK will oversee a new three-week training programme for Ukrainian soldiers, as he visited Kyiv for the third time this year for talks with the Ukrainian president, Volodymyr Zelenskiy.

The prime minister had been expected to address Conservative MPs at the Northern Research Group conference in Doncaster on Friday, but pulled out at the last minute.

It later emerged he had travelled to Kyiv. Beset by challenges at home – including the resignation of his ethics adviser, Christopher Geidt, on Wednesday – Johnson is well-liked in Ukraine, where he is seen as having led western opposition to Russia’s brutal invasion.

In a statement released by No 10, Johnson said: “As Ukrainian soldiers fire UK missiles in defence of your nation’s sovereignty, they do so also in defence of the very freedoms we take for granted. That is why I have offered President Zelenskiy a major new military training programme that could change the equation of this war – harnessing that most powerful of forces, the Ukrainian determination to win.”

The UK has provided £1.3bn worth of economic and military support to Ukraine, including anti-tank missiles, armoured vehicles and plastic explosives. But Ukraine’s armed forces have been pressing for training on western military kit, as well as more heavy weapons. Kyiv wants a rapid influx of expertise and equipment so it can try to start pushing Russia back before the weather turns.

The new training programme announced by Johnson will involve UK-led courses lasting three weeks, and include battle skills, basic medical training, cybersecurity and counter-explosive tactics. The courses will take place outside Ukraine, most likely in Poland.

Zelenskiy’s official spokesperson, Andriy Yermak, said that at the meeting with “Boris”, they had discussed “the much-needed heavy weapons and air defence systems supplies, economic support for Ukraine” and “increasing sanctions pressure on the Russian Federation”.

Johnson said: “Two months on from my last visit, the Ukrainian grit, determination and resilience is stronger than ever, and I know that unbreakable resolve will long outlive the vain ambitions of President Putin.”

The prime minister’s visit followed a meeting between Zelenskiy and key European leaders, including the French president and German chancellor, earlier this week.

On Friday, the European Commission signalled its support for Ukraine to become a candidate country – the first step towards joining the EU. The commission’s president, Ursula von der Leyen, told a press conference: “Ukrainians are ready to die for the European perspective. We want them to live with us the European dream.”