British Prime Minister Rishi Sunak visited wartime Kyiv on Friday to sign a new security agreement and announce an increase in military funding for Ukraine to buy drones, including surveillance, long-range strike and sea drones.

Britain, one of Ukraine's closest allies during the Russian invasion, will increase its support in the next financial year to 2.5 billion pounds ($3.19 billion), an increase of 200 million pounds on the previous two years, Sunak said.

"Our opponents around the world believe that we have neither the patience nor resources for long wars. So waver now, and we embolden not just Putin, but his allies in North Korea, Iran and elsewhere," Sunak told a press conference.

His trip comes at an important juncture for Kyiv in the nearly two-year-old war as political infighting in the United States and European Union has held up two major packages of assistance.

Kyiv has relied heavily on military and financial aid from the West since the Russian invasion in February 2022.

President Volodymyr Zelenskiy told the press conference he felt vital US financial assistance would materialize and that he felt more positive now than last month.

The two leaders signed what Zelenskiy described as an "unprecedented security agreement" - an arrangement the Ukrainian leader said would remain in place until Kyiv joined the NATO military alliance.

"This is not simply a declaration," Zelenskiy wrote on social media platform X.

His chief of staff, Andriy Yermak, said the agreement set out the support that London would continue to provide, including intelligence sharing, medical and military training, and defense industrial cooperation.

The UK-Ukraine Agreement on Security Cooperation follows an earlier agreement by the Group of Seven nations to provide Ukraine with bilateral security guarantees.

Ukrainian lawmakers posted short video clips of Sunak addressing members of parliament in Kyiv and receiving a standing ovation.

Britain said it would provide the largest delivery of drones to Ukraine from any nation, with most of them expected to be manufactured in Britain.

Ukraine had been fighting for the principles of freedom and democracy for two years, Sunak said in a statement.

"We will stand with Ukraine, in their darkest hours and in the better times to come."