Sir Keir Starmer and Volodymyr Zelensky have agreed to "maintain momentum and continue working intensively" on efforts to secure peace in Ukraine during their meeting in Rome.
The two leaders met on Saturday following Pope Francis's funeral.
They discussed recent advances towards ending the Ukraine war, according to Downing Street.
The meeting came after Zelensky had earlier met with President Donald Trump within St Peter's Basilica before the funeral ceremony began.
Prime Minister Keir Starmer and President of Ukraine Volodymyr Zelensky
PA
Donald Trump and Volodymyr Zelensky met ahead of the funeral REUTERSThe Prime Minister and Ukrainian President were pictured alongside France's Emmanuel Macron and the American President during the Vatican encounter. Trump has claimed a peace deal is "very close" to being agreed.
He suggested Ukraine and Russia now need to meet at "a very high level" for talks.
A Downing Street spokesman said the leaders "discussed positive progress made in recent days to secure a just and lasting peace in Ukraine".
They "agreed to maintain momentum and continue working intensively with international partners to drive forward the next stages of planning."
LATEST ON THE RUSSIA-UKRAINE WAR
Prime Minister Keir Starmer and President of Ukraine Volodymyr Zelensky with wife Victoria
PA
Clergymen bid their final farewell to Pope Francis as he was laid to restVatican MediaThe US has been pressing Ukraine to accept a peace deal which would require Kyiv to accept Russian control of vast swathes of occupied land, a position rejected by Zelensky's government.
The Ukrainian leader also refuses to accept continued Kremlin control in Ukraine's south and east. Instead, he has called for Russian President Vladimir Putin to accept an unconditional end to the fighting.
Following the funeral ceremony, Zelensky described his face-to-face encounter with Trump as a "good meeting".
It was their first meeting since a reportedly difficult clash at the White House in February. In a post on social media, the Ukrainian leader said: "We discussed a lot one-on-one. Hoping for results on everything we covered."
World leaders congregated in Rome to attend the funeral
GETTYHe emphasised their talks focused on "protecting lives of our people" and achieving a "full and unconditional ceasefire". Zelensky called it a "very symbolic meeting that has potential to become historic".
Trump later criticised Zelensky in a post on his Truth Social website, claiming that his desire to see Crimea returned to Ukraine was among "other ridiculous requests".
The US President also condemned Putin, whose forces continue to bombard civilian areas. Trump wrote: "There was no reason for Putin to be shooting missiles into civilian areas, cities and towns, over the last few days."
He suggested Putin "maybe doesn't want to stop the war" and "has to be dealt with differently, through 'Banking' or 'Secondary Sanctions'".
A further meeting between Zelensky and the American president was expected, but Trump left Vatican City not long after the funeral concluded.
The Downing Street spokesman confirmed that the Prime Minister and Ukrainian President "agree to speak again at the earliest opportunity".
