By Olena Harmash KYIV (Reuters) -British Prime Minister Keir Starmer said on Thursday he would give Ukraine the support it needed to put it in the strongest position to fight Russia in 2025, saying before talks in Kyiv with President Volodymyr Zelenskiy: "We mustn't let up".

Britain has been at the forefront of western countries offering military support for Ukraine since Russia’s full-scale invasion began in February 2022, but the question of whether the UK would put troops on the ground to help guarantee any peace deal will be a big test for Starmer.

British Prime Minister Keir Starmer arrived in Ukraine Thursday with a pledge to help guarantee the country’s security for a century, days before Donald Trump is sworn in as US president.

British Prime Minister Keir Starmer pledged on Thursday to work with Ukraine and allies to offer Kyiv robust security guarantees if a ceasefire is negotiated with Russia, offering more support to President Volodymyr Zelenskiy with a 100-year partnership deal.

The UK Prime Minister has traveled to Kyiv to finalize a "landmark 100-year partnership" with Ukraine, formalizing economic and military support already pledged.