British Prime Minister Boris Johnson held talks in Kyiv with Ukraine's President Volodymyr Zelensky on Saturday.
The office of the British prime minister said the visit was a "show of solidarity" with the Ukrainian people, reports BBC.
A spokesman said Boris Johnson was using the trip to set out a new package of financial and military aid.
It comes the day after the UK announced £100m of weapons for Ukraine after the bombing of refugees at a railway station.
The spokesman said: "The prime minister has travelled to Ukraine to meet President Zelensky in person, in a show of solidarity with the Ukrainian people," he said.
"They will discuss the UK's long-term support to Ukraine and the PM will set out a new package of financial and military aid."
A photograph of the meeting was posted online by the Ukrainian embassy in London.
In a Facebook post, Andriy Sybiha, deputy head of the Ukrainian president's office said: "The UK is the leader in defence support for Ukraine. The leader in the anti-war coalition. The leader in sanctions against the Russian aggressor."
Johnson is the latest Western leader to travel to the Ukrainian capital for talks with the country's president.
European Commission President Ursula von der Leyen and the EU's foreign policy chief Josep Borrell both made visits on Friday, and Austrian Chancellor Karl Nehammer earlier on Saturday.