Andy Burnham will mark his first foreign visit as prime minister with a trip to Kyiv on Monday to reiterate the UK's support for Ukraine and honour the country's independence day.
The prime minister will chair his first meeting of the "coalition of the willing", set up by the UK and France under his predecessor, Sir Keir Starmer.
He is also set to accept an award on behalf of the British people recognising the UK's support for Ukraine and to take part in independence day events.
Burnham will be reaffirming the UK's backing for Kyiv in the wake of escalating Russian strikes on Ukraine in recent weeks - including one on a shopping centre on Friday that killed at least 16 people.
Ahead of Monday's visit, Burnham said: "On Ukraine's 35th anniversary of independence, the Ukrainian people should be in no doubt: the UK is behind you today and for as long as it takes.
"I am proud of the contribution our country has made to Ukraine and I want the Ukrainian people to hear it directly from me that our support will not waver. After all, Ukraine's security is our security."
He said the friendship Ukraine shared with the UK would "long outlast Russia's illegal war", adding: "Russia should be in no doubt of our resolve. We will not back down until there is a just and lasting peace."
It comes after Moscow warned of "consequences" over the use of British drones by Ukraine in its recent ramping up of strikes on Russian infrastructure.
Kyiv has stepped up long-range attacks on Moscow and other Russian regions, targeting oil refineries and warehouses of the country's largest online retailer, Wildberries.
The Russian embassy in the UK has accused Britain of "deliberately opting for an escalation of the Ukraine crisis", saying "the deeper its involvement in the conflict... the higher the price it will pay".
In response, Burnham said last week: "We are not fair-weather friends, we will be there in Ukraine's hour of need and that won't change."
Asked on Tuesday about the Russian threat, Burnham maintained the UK was "providing support so that Ukraine can defend itself and that's been the British position all the way through this conflict, by previous prime ministers - it remains the case with me".
Burnham is also set to announce that the government has agreed to allow defence company MBDA to declassify information on UK components for the long-range Scalp missile – the French equivalent of the UK's Storm Shadow.
Both missiles use shared British and French technology, and President Emmanuel Macron is looking at setting up local assembly lines for Scalp missiles in Ukraine.
Zelensky was the first foreign leader to be welcomed to Downing Street after Burnham became prime minister in July.
The visit comes as Russia confirmed its ambassador to the UK, Andrei Kelin, had left his post in London in recent weeks.
The Kremlin is yet to put forward a replacement but Russia's embassy to the UK told the BBC it did not reflect an intention to downgrade diplomatic relations between the two nations.
Source: BBC
-Agencies
