Ukraine's allies will support the country for "as long as it takes", Foreign Secretary James Cleverly will say when he addresses the UN Security Council later.
The meeting comes a year on from the Russian invasion of Ukraine, with the anniversary due to be marked in the UK and countries around the world.
Speaking at a special session of the UN Security Council, Mr Cleverly is expected to stress the need to send a "clear message" that Ukraine will be backed for as long as is required, with the conflict showing no sign of ending soon.
"One year into this terrible war, let us send this clear message: our support for Ukraine is not, and will never be, time-limited.
"We will keep the promises we made to the UN Charter and the Ukrainian people, and will give the Ukrainians all the help they need for as long as it takes until Ukraine prevails," the Foreign Secretary will say.
Mr Cleverly is set to meet his Ukrainian counterpart Dmytro Kuleba, as well as UN Secretary General Antonio Guterres, while in New York.
UK's Ukraine support
Over the last year, the UK has been among the most vocal supporters of Ukraine's efforts to push back the Kremlin's troops, with Prime Minister Rishi Sunak announcing earlier this year that Britain would be the first country to supply tanks to its armed forces.
Mr Sunak said 14 Challenger 2 tanks will be supplied, with the land vehicles set to arrive in eastern Europe next month.
Ukrainian tank drivers have described how significant the British Challenger 2 tank will be in the war with Russia.
Defence Secretary Ben Wallace visited Bovington Camp in Dorset and took a ride on a training vehicle being used to teach experienced Ukrainian personnel how to handle the Challenger 2 battle tank.
A Ukrainian tank driver, known as Sacha, said: "The Challenger tank is a very formidable and strong tank; it has got a very good defence system and cannon. It will make a great lot of difference."
Ukraine has over the last 12 months benefited from a broad coalition of support led by the US, the UK and a host of European states amid international condemnation of Russia's invasion.
The security council meeting follows a session of the UN general assembly on Thursday, at which the conflict in Ukraine was centre stage.
The UN General Assembly on Thursday approved a non-binding resolution, backed by 141 nations, calling for Russia to end hostilities in Ukraine and demanding the withdrawal of its forces.
Yet there are fears that as winter turns to spring, and with Russian President Vladimir Putin showing no sign of relenting, the war could drag on for at least another year.
Mr Cleverly said: "When Putin invaded Ukraine on February 24 2022, he expected his brutal assault to succeed and international support to crumble within weeks. He has been proven gravely wrong.
"Twelve months on, the international community remains resolute that Ukraine will win the war, end Russia’s threat to Ukraine's sovereignty and forge a sustainable peace.
"Ukraine is turning the tide and Putin is losing. One year into this terrible war, our support will continue for as long as it takes."