Rishi Sunak has promised the UK’s largest ever military support package for Ukraine as he warned that Vladimir Putin would “not stop at the Polish border” if Russia won the war.

The prime minister will visit Poland on Tuesday to discuss European security and the threat from Russia with the Polish leader, Donald Tusk, and the Nato secretary-general, Jens Stoltenberg, before travelling to Germany to meet the chancellor, Olaf Scholz.

The UK plans to give vital equipment to Kyiv including 400 vehicles, more than 1,600 missiles, 4m rounds of ammunition, 60 boats, as well as an additional £500m in military funding, taking the total to £3bn this financial year.

“Defending Ukraine against Russia’s brutal ambitions is vital for our security and for all of Europe. If Putin is allowed to succeed in this war of aggression, he will not stop at the Polish border,” Sunak said ahead of the trip.

“Ukraine’s armed forces continue to fight bravely, but they need our support – and they need it now. [This] package will help ensure Ukraine has what they need to take the fight to Russia.

“The United Kingdom will always play its part at the forefront of European security, defending our national interest and standing by our Nato allies.”

The UK has to date pledged almost £12bn in support to Ukraine since February 2022, of which £7.1bn is for military assistance and the rest humanitarian and economic support.

His announcement comes as the US House of Representatives, after months of stalling, finally approved a $61bn package of new military aid for Ukraine to help combat Russia’s invasion, after a fierce battle within the Republican party.

The UK’s £500m additional funding, which officials said would come from Treasury reserves, will be used to deliver ammunition, air defence, UK-built drones and engineering support to the Ukrainian frontline.

The Ministry of Defence will also send what was described as the largest-ever single package of equipment from the UK to help push back the Russian invasion on air, land and sea. It is unclear how much this will cost, but will come from existing MoD budgets.

The package includes 60 boats with offshore raiding craft and dive boats; more than 1,600 strike and air defence missiles; more than 400 vehicles, including 160 protected mobility “Husky” vehicles and 162 armoured vehicles; as well as nearly 4m rounds of small arms ammunition.

The defence secretary, Grant Shapps, said: “This record package of military aid will give President Zelenskiy and his brave nation more of the kit they need to kick Putin out and restore peace and stability in Europe.

“We will never let the world forget the existential battle Ukraine is fighting, and with our enduring support, they will win.”

At his first in-person meeting with the new Polish prime minister, Sunak will also seek to deepen UK-Poland ties, building on existing defence and security cooperation. He will also offer to deploy an RAF Typhoon squadron to carry out Nato air policing over Poland next year.

There are about 400 British troops based in Poland full-time, while about 8,000 have taken part in Nato exercise Steadfast Defender in Poland, the alliance’s largest since the cold war.