The prime minister also announced plans to train Ukrainian fighter jet pilots as part of a long-term UK investment in its ally.
Boris Johnson has criticised Mr Sunak’s decision not to send fighter jets after No 10 said last week that it was “not practical” to send British aircraft to the warzone.
Mr Sunak said on Wednesday that he was “proud” to announce an expansion in training from soldiers to fighter jet pilots and marines, “ensuring Ukraine has a military able to defend its interests well into the future”.
The prime minister said: “President Zelensky’s visit to the UK is a testament to his country’s courage, determination and fight, and a testament to the unbreakable friendship between our two countries.”
“Since 2014, the UK has provided vital training to Ukrainian forces, allowing them to defend their country, protect their sovereignty and fight for their territory,” Mr Sunak said.
He added: “It also underlines our commitment to not just provide military equipment for the short term, but a long-term pledge to stand shoulder-to-shoulder with Ukraine for years to come.”
The audience between the King and Mr Zelensky will take place at Buckingham Palace this afternoon. Mr Zelensky will also use his surprise visit to inspect Ukraine’s troops being trained by the British armed forces.
The expansion of the UK’s training to include jet fighter pilots is significant as Mr Zelensky has been urging Western nations to supply planes. The UK has so far refused, arguing that the RAF’s F-35 and Typhoon jets take too long for pilots to train on.
But the announcement by No 10 signals a shift. Officials said that “as part of that long-term capability investment” the UK will work with Ukraine and international allies “to co-ordinate collective support to meet Ukraine’s defensive needs”.
Ukrainian troops are already being trained in the use of Challenger 2 tanks, expected to be sent to the country next month. Mr Sunak will offer longer-range firepower to help counter Russia’s ability to strike at Ukraine’s towns and energy plants.
Mr Johnson made a surprise fourth visit to Ukraine last month, despite warnings from senior military figures that he should stop “looking for publicity” and could upstage Mr Sunak. The current PM visited Kyiv in November.
Mr Zelensky gave a historic virtual address to the Commons in March 2022, echoing Winston Churchill and comparing his country’s fight to Britain’s battle against the Nazis.
The Ukrainian president visited Washington in December, giving a 20-minutes speech to Congress in which he vowed that his country would “never surrender” and thanked Americans for helping fund the war effort.
Meanwhile, a Labour MP has proposed a new law so Russian state assets frozen in the UK should be seized and used to help rebuild Ukraine.
Former minister Sir Chris Bryant said it would set a precedent aimed at deterring other states waging a “war of aggression” against another self-governing state.
MPs heard Ukraine estimates Russia has caused one trillion US dollars of damage since the start of the full-scale invasion in February 2022, which does not include costs associated with territory invaded in 2014.