British Prime Minister Rishi Sunak visited Kyiv on Friday to announce an increase in military funding to help Ukraine purchase new military drones, including surveillance, long-range strike and sea drones.
London has been one of Kyiv's closest allies during Russia's invasion and Sunak said Britain would increase its support in the next financial year to £2.5 billion ($3.19 billion), an increase of £200 million on the previous two years.
"I am in Ukraine to deliver a simple message. Our support cannot and will not falter," Sunak wrote on social media platform X.
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 full-scale invasion in February 2022.
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.
"The Ministry of Defence will work with international partners to significantly scale up the number of drones provided for Ukraine's defence," a UK government statement said.
Sunak's office said the two countries would also sign a UK-Ukraine Agreement on Security Cooperation, following on from an agreement by the Group of Seven nations to provide Ukraine with bilateral security assurances.
Britain said the agreement "formalises a range of support the UK has been and will continue to provide for Ukraine's security, including intelligence sharing, cyber security, medical and military training, and defence industrial cooperation".
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."