British Prime Minister Keir Starmer met with Ukrainian President Volodymyr Zelensky in Kiev on Thursday, in a show of solidarity four days before the inauguration of Donald J. Trump.

Trip to Ukraine, first Mr. Starmer’s move since becoming prime minister over the summer comes amid a flurry of diplomacy between Kiev and its European allies, who are watching whether Mr. Trump to keep US support for Ukraine in war against Russia.

Britain is the third largest provider of military aid to Ukraine, after the United States and Germany, and on Thursday Mr. Starmer and Mr. Zelensky signed a “100-year partnership” between their two countries.

“We have reached a new level – this is more than a strategic relationship,” said Mr. Zelensky, according to Ukrainian media.

The agreement will include a special focus on maritime security and promises to strengthen cooperation in the fields of technology, healthcare and education. It follows a tighter security agreement signed a year ago in response to an invasion ordered by Russian President Vladimir V. Putin in 2022.

“Putin’s ambition to separate Ukraine from its closest partners was a monumental strategic failure,” Mr. Starmer it is stated in the press release. “Instead, we’re closer than ever.”

Mr. Trump said he plans to end the war quicklybut he did not say how he would do it. Marco Rubio, his choice for secretary of state, said as much this week both Russia and Ukraine would have to make concessions in any negotiations.

Kiev’s official position is that it will not negotiate directly with Mr. Putin, which Ukrainian Foreign Minister Andriy Sybiha confirmed on Wednesday. But Mr. Zelenski said that he hopes to meet with Mr. Trump as soon as possible.

on Thursday, Valerij ZaluzniUkraine’s ambassador to Britain and former commander-in-chief, accompanied Mr Starmer on the visit. He said the partnership will deepen security ties and strengthen cooperation between the two countries.

Mr Zelensky told a meeting of allies in Germany this month that he planned to speak to Mr Starmer “in the coming weeks” about the possibility of Britain sending peacekeepers to Ukraine. Ukrainian leader too presented the idea to other European leadersbut they met it with skepticism.

Ukraine received support from other European allies in other ways.

German Defense Minister Boris Pistorius he said during a visit to Kiev on Tuesday he said he was optimistic Berlin would find a way to send an additional 3 billion euros (about $3.1 billion) in military aid. But Germany is facing its own political upheaval after the government crashed a month ago.

Mr Zelensky discussed the continuation of French military support for Ukraine with President Emmanuel Macron in a telephone conversation this week, according to Mr. Zelenski’s officeand the Latvian delegation visited Ukraine on Tuesday to discuss military and humanitarian aid.

And on Wednesday, Mr. Zelenski was in Warsawwhere he met with Polish Prime Minister Donald Tusk and its President Andrzej Duda. Both expressed support for Ukraine’s efforts to join NATO, the prospect of that military alliance he was hesitant to fully endorsedespite offering significant support to Kiev.

Ukraine has stepped up its diplomatic efforts as the Russian offensive continues in the Donetsk region of eastern Ukraine.

The last modest gains Ukraine made during its counteroffensive in the summer of 2023 were wiped out, according to an assessment Wednesday by DeepState, an analysis group with ties to the Ukrainian military, after Russian forces captured the village of Neskuchne.

Moscow forces are also making progress in their attempts to surround the key city of Pokrovskalso in eastern Ukraine, from the south.

While Mr. Starmer was visiting Kiev, the capital of Ukraine was under air alert. Soon after, a loud bang was heard in the sky above the city. Vitaliy Klitschko, the mayor, said air defenses were working and warned residents to stay in shelters.

The British leader and Mr. Zelensky visited the burn unit at the hospital where wounded soldiers and civilians are treated. After Mr. Introduced by Starmer, Petro, a civilian with burns on his hands and arms, asked: “Prime Minister of Britain, right?” and then added: “If Ukraine falls, so does Europe.”

Mr Starmer said the injuries he saw at the hospital were “a sad reminder of the high price Ukraine is paying.”

Naralija Novosolova i Cassandra Vinograd contributed reporting.