Prime Minister Liz Truss says the UK will match, or exceed, the military aid it has given to Ukraine this year in 2023.
The commitment means the UK will spend at least £2.3 billion next year on military aid to help Volodymyr Zelenskyy’s “inspirational” troops.
Ahead of a meeting at the UN General Assembly in New York, Ms Truss pledged the UK's ongoing commitment to Ukraine as it fights a Russian invasion launched at the end of February.
She will also urge world leaders to end reliance on Russian oil and gas, which continues to be exported to Europe in a trade worth billions of dollars.
In a statement, the UK described itself as the second-largest donor to Ukraine, after the United States.
"We have trained 27,000 members of the Ukrainian Armed Forces since 2015, and in the last year we have provided hundreds of rockets, five air defence systems, 120 armoured vehicles and over 200,000 pieces of non-lethal military equipment," said the statement.
"Last week saw the largest commercial road move of ammunition since the Second World War as tens of thousands more rounds of UK-donated artillery ammunition went to the front lines in Ukraine."
Ms Truss's comments come after huge Ukrainian gains in the conflict, with a successful counteroffensive against Russian positions in the Kharkiv region.
Ukraine's President, Volodymyr Zelenskyy, says his troops have recaptured thousands of square miles worth of territory in recent weeks.
The prime minister described recent Ukrainian success as "inspirational."
"Time and time again these brave people have defied the doubters and showed what they can do when given the military, economic and political support they need.
“My message to the people of Ukraine is this: the UK will continue to be right behind you every step of the way. Your security is our security.”
193 UN member states will be meeting this week, with the war in Ukraine expected to be a major talking point, along with global food insecurity and climate change.
Both Russia and Ukraine will have representatives at the meeting - although they have no plans to meet.