Sir Keir Starmer has pledged to put Ukraine in the “strongest possible position” this year as he made his first trip to Kyiv as prime minister.

He said the UK would “never let up” on giving the necessary support to Ukraine in signing what Downing Street says is a “landmark 100-year partnership” pact with Ukraine.

“Today is a truly historic day, our relationship is closer than ever,” Ukrainian President Volodymyr Zelensky told reporters. The agreement formalises economic and military support already pledged to the country.

Zelensky is keen to firm up security guarantees from key allies, wary that Donald Trump’s new US administration could start pushing Ukraine to make peace with Russia.

The deal announced on Thursday includes economic aid, support for healthcare, and increased military collaboration on maritime security and drone technology.

Unlike other prime ministers who rushed to Kyiv, Sir Keir took his time to visit, having visited previously as opposition leader.

But after six months in office he came to Ukraine pledging long-term support to help fight what he called Russia’s “illegal and barbaric invasion”.

In Kyiv, the two leaders walked behind an honour guard which carried wreaths in the national colours of the UK and Ukraine.

After soldiers set down the wreaths, Sir Keir and President Zelensky placed their bouquets at the foot of the wall outside St Michael’s Golden-Domed Monastery.

The Kyiv landmark is covered in photos of the dead and has become a place of pilgrimage for grieving families to pay tribute.

As the leaders met for talks inside Kyiv’s Mariinsky palace, multiple explosions and air raid sirens could be heard.

The air raid was “a reminder of the daily attacks and the resolve of the Ukrainian people in the face of it”, Sir Keir said.

Shortly after, when asked by reporters at a press conference what he thought about the ‘hello’ from Russia, Zelensky replied that Ukraine would send its own ‘hello back’.

“We are with you not just today, for this year or the next – but for 100 years – long after this terrible war is over and Ukraine is free and thriving once again,” Sir Keir told the Ukrainian president.

The prime minister also visited an apartment building damaged in a New Year’s Day drone attack, which killed a couple who had been prominent scientists.

The apartment is just down the street from the president’s office.

“They were sending us a message,” the head of Kyiv’s military administration told Sir Keir. “No one is safe”.

Sir Keir also visited a school, partnered with a sister school in Liverpool, and a hospital in Kyiv specialising in treating burns.

On the tour of the intensive care unit, he met wounded Ukrainians on a rehabilitation ward supported by the British Red Cross.

“If Ukraine falls, so does Europe,” an injured civilian who had burns across both hands and arms told the prime minister.

Sir Keir said the injuries he saw were “a grim reminder of the heavy price that Ukraine is paying”.

“One of the consequences of this conflict has been to draw Nato more strongly together,” he said.

The prime minister added support for Ukraine was “bigger and stronger than it has been, and we must stand behind Ukraine for as long as it takes”.

“We must never let up on that and we’ve been leading the way,” he said.

Trump’s choice to become secretary of state, Marco Rubio, said earlier this week that Russia and Ukraine would both have to make concessions to see an end to the war.

Zelensky has previously said he is looking to the UK for help getting security guarantees to deter future attacks.

Joining Nato is near the top of his wish list, but Ukraine also wants its allies to send peacekeepers to the country if fighting does stop, to patrol the current frontline which could become a buffer zone in any peace agreement.

Ahead of the visit, Zelensky had said he would discuss with the prime minister.

The latest pledges build on £12.8bn of support the UK has already given to Ukraine. It has also already committed to giving the country £3bn in military aid every year for “as long as it takes”.

Russian forces are gaining ground more quickly than at any time since the country launched its full scale invasion of Ukraine in 2022, despite Ukrainian strikes on Russia.

According to latest reports from reputable Ukrainian open source material, Russia has cut off a key highway and railway to the south-west of Pokrovsk, a strategically important hub in eastern Ukraine. Ukraine says most of Russia’s attacks in the past 24 hours focused on the town.

They have also made big advances in other big population centres in the east – in Toretsk and Chasiv Yar.

As the invasion reaches the end of its third year, with an estimated million people either killed or wounded, Ukraine is losing territory in the east.

Ukraine has already been using British-supplied Storm Shadow missiles to attack Russian military facilities far from the border.

The change to allow their use in Russian territory late last year was welcomed by Kyiv, and slammed by Moscow.

The partnership, formed of a treaty and a political declaration, is due to be presented to Parliament in the coming weeks.

Plans for it began under the previous Conservative government.

While this is his first visit as prime minister, Sir Keir visited Ukraine when he was leader of the opposition in 2023, and has hosted President Zelensky twice at Downing Street since entering office.

Additional reporting by Alex Smith and Zahra Fatima