The prime minister will use a trip to the Baltic region to urge fellow leaders to stand firm in their support for Ukraine as he pledges a new stream of defensive aid to guard against Russian aggression.
First jetting off to a meeting of northern European allies in Latvia, Rishi Sunak will call on his counterparts to sustain or boost their current offers.
The prime minister will then travel to Estonia to meet British troops and sign a new technology digital partnership with the nation’s prime minister.
It comes as the UK has announced a fresh supply of hundreds of thousands of rounds of artillery ammunition as part of its package of defensive aid for 2023, under a £250m contract.
At the meeting in Riga on Monday, the members of the Joint Expeditionary Force (JEF) are expected to discuss Ukraine’s defence needs while seeking to accelerate their own co-operation.
Following the gathering, which will be addressed by Ukrainian president Volodymyr Zelensky, Mr Sunak will meet Latvian prime minister Krisjanis Karins.
In Estonia, he will meet UK and Nato troops serving on alliance’s eastern flank.
The new digital partnership, which Mr Sunak will sign with Estonian prime minister Kaja Kallas, will see the countries strengthen ties across health, education, cyber security, data and connectivity.
Mr Sunak said: “From the Arctic Circle to the Isle of Wight, the UK and our European allies have been in lockstep in our response to the invasion of Ukraine, and we remain steadfast in our ambition for peace in Europe once again.
“But to achieve peace, we must deter aggression and our deployments across the region together are vital in ensuring we are able to respond to the gravest of threats.
“I know this Joint Expeditionary Force summit will only underline our close friendships and unwavering support for Ukraine.”
The JEF alliance includes Denmark, Finland, Estonia, Iceland, Latvia, Lithuania, the Netherlands, Sweden and Norway.