Britain will increase their financial support for Ukraine to £2.5bn over the coming year, Rishi Sunak has announced.
The PM pledged Britain's largest annual commitment since Russia's invasion, following a face-to-face meeting with President Volodymyr Zelensky in Kyiv.
The new agreement in support of Ukraine's long-term security will provide them with equipment such as long-range missiles and artillery shells; as well as air defence.
Around £200m will be invested in drones – most of which will be manufactured in the UK.
Since Russia invaded their neighbours in February 2022, The UK has committed £4.6 billion in military assistance to Ukraine, as well as hosting a training programme (Operation Interflex), which is supported by several allies, to train 30,000 new and existing Ukrainian personnel.
Downing Street said this latest package of support would form the first step in what it called "an unshakeable hundred-year partnership between Ukraine and the UK".
It will also include £18m for humanitarian aid, help fortify Ukraine's energy infrastructure and more funding for online English language training.
Mr Sunak, who last visited Ukraine 15 months ago in November 2022, said: "I am here today with one message: the UK will also not falter. We will stand with Ukraine in their darkest hours and in better times to come."
"The UK is already one of Ukraine's closest partners because we recognise their security is our security," he added.
"Today we are going further, increasing our military aid, delivering thousands of cutting-edge drones and signing a historic new security agreement to provide Ukraine with the assurances it needs for the long term."
The prime minister continued: "For two years, Ukraine has fought with great courage to repel a brutal Russian invasion. They are still fighting, unfaltering in their determination to defend their country and defend the principles of freedom and democracy."
The UK's commitment comes after months of pressure from MPs, who argued the government should have given Ukraine greater clarity much earlier so it could develop its military planning.
However, other allies are struggling to agree on suitable support measures for Ukraine, who are in desperate need of supplies as the war closes in on the two-year mark.
Today, a Russian missile hit a hotel in Kharkiv, injuring 13 people.
In the US, rising opposition to continued financial aid has seen Republicans block a $60bn (£47bn) package of support for Ukraine, in an attempt to increase spending on tackling migration along America's southern border.
And in the EU, Hungary's prime minister, Viktor Orban, has blocked a €50bn (£43bn) support package for Ukraine amidst a funding row with Brussels.
The UK's commitment comes at a tense moment in global conflict, as they joined the US in launching air and missile strikes today in Houthi-controlled areas of Yemen, aimed at halting attacks on ships in the Red Sea.
In the Middle East, Israel continues to bombard Gaza as part of its ongoing war against Hamas.
South Africa says Israel is committing genocide against the Palestinians in its war in Gaza, outlining the case to the International Court of Justice (ICJ) this week.
It is also asking the court to order Israel to halt its military activity.
Today, Israel accused South Africa of presenting "a sweeping counter-factual description" of the Israel-Palestinian conflict, Israeli lawyer Tal Becker told the ICJ.
