Keir Starmer has announced a "historic" 100-year partnership with Ukraine, saying the UK will support the country "beyond this terrible war" and towards a future "free and prosperous again".

Starmer, on his first visit to Kyiv as prime minister, said the unprecedented deal reflected the "huge feeling between our two countries". He added that "Putin currently shows no sign of wanting to stop" his "relentless aggression."

This was dramatically underlined when a Russian drone flew over Zelensky's Mariinsky Palace in Kiev as the two leaders were holding talks. Anti-aircraft fire erupted as drones buzzed overhead.

A loud roar was heard as Ukrainian air defense forces tried to shoot it down. City officials said there were no injuries, but falling debris damaged a car.

Starmer said the attack was a reminder of what Ukrainians go through every day. "This is real for us," he said. "This is a threat that Ukraine faces every day, and the determination and determination are incredible."

Asked by Ukrainian reporters about "greetings from Moscow" in the air, Zelensky told a joint news conference: "We will also say hello to them."

The century-old partnership comes at a precarious time for Ukraine as Donald Trump is sworn in in the United States on Monday. He has vowed to end the war quickly and is expected to meet Vladimir Putin early in his presidential term.

Starmer did not comment directly on how Britain would respond if the new White House dropped military support for Ukraine or forced Ukraine to strike a deal that would benefit Moscow. Instead, he praised Washington's "vital" aid to Kyiv. "We will continue to work with the United States today, tomorrow and into the future," he said.

The UK-Ukraine deal includes £3bn of annual support from the UK and will continue indefinitely. Starmer said Britain would step up training for Ukrainian soldiers, provide mobile air defense systems and deliver 150 artillery barrels made at Sheffield Forge - the first production of artillery barrels in 20 years.

In recent months, Ukraine has been losing territory at the fastest pace since Russia's full-scale ground invasion in 2022. Starmer acknowledged that the country was not in the "strongest position" ahead of possible talks and that it needed strong security guarantees to deter future aggression.

Zelenskiy said he was in discussions with several European countries, including France, Britain and Poland, where Starmer will visit on Friday, about international peacekeeping forces. But he said it was too early to talk about details before Trump returns to the Oval Office.

Starmer told Sky News: "Well, I've been discussing this with a number of allies, including of course President Macron, including President Zelensky who is here today, and we will play our full part. We have always been a key player in the defense of Ukraine "

Zelensky stressed that Ukraine's best security guarantee is to join NATO. He said four countries opposed Kyiv's accession: the United States, Germany, Slovakia and Hungary. Starmer said Ukraine was on an "irreversible path" to join the alliance.

Earlier, the two leaders visited the golden-domed St. Michael's Monastery in Kiev. They laid flowers on the wall to commemorate the thousands of service members killed in the war with Russia, displaying burned-out enemy tanks next to them.

The prime minister also met soldiers at a hospital specializing in treating burns and visited a building where two prominent scientists were killed when a drone struck their upper-floor apartment on January 1.

The building is located down the street from the Presidential Office. Timur Tkachenko, the head of Kiev's military junta, told Starmer: "They are sending us a message - no one is safe."

Ahead of Thursday's meeting, Starmer described Putin's ambitions to wrest Ukraine away from his closest partners as a "huge strategic failure". "Instead, we are closer than ever and this partnership will take that friendship to the next level," he said.

"The strength of our long-standing friendship cannot be underestimated. Supporting Ukraine to resist Russia's brutal invasion and rebuild a prosperous, sovereign future is critical to this administration's security foundation and our plan for change."

Zelensky acknowledged at a press conference on Thursday that his forces had been pushed back in the east of the country, but said he was optimistic that the situation could "stabilize", as it had in other parts of the front line.

The Russian president has given no indication of willingness to end the fighting. His demands are as extreme as ever, including the handover of four Ukrainian regions he "annexed" in 2022, including territory that Moscow does not control; a veto on Kyiv's membership of NATO; and the replacement of Zelensky's government with a pro-Kremlin government .

His apparent calculation is that Trump will quickly end military aid to Ukraine, which will bring further gains. For the first time, Russian troops are approaching the Dnipropetrovsk region, the center of Ukraine's defense production.

Starmer was at Checkers last week to discuss the direction of the conflict with French President Emmanuel Macron following Trump's return. The two leaders spoke about the importance of providing security guarantees to Ukraine.

The One Hundred Year Partnership also aims to strengthen economic ties in non-military areas such as science, technology and culture. Starmer will announce £40 million in funding for economic recovery, which the government says will create opportunities for British businesses.

A senior Ukrainian official expressed frustration with Starmer's new government in November and suggested relations with Britain had "regressed". Supplies of Britain's long-range Storm Shadow missiles have been halted, the official said, adding that the prime minister had repeatedly postponed a visit to Kiev.

"That didn't happen. Starmer didn't give us long-range weapons. Things are not the same now as they were when Rishi Sunak was chancellor. The relationship has gotten worse," the official told the Guardian. Downing Street reacted angrily to the comments and declined to comment on operational matters.

Ukraine subsequently used Storm Shadow missiles against high-value targets, including in Kursk Province. Ukrainian troops launched a small counterinvasion into Russia's border region five months ago and recently captured two North Korean soldiers.