LONDON (Reuters) -Volodymyr Zelenskiy and British Prime Minister Keir Starmer announced a new defence co-production initiative on Monday during a short visit by the Ukrainian president to London to discuss his country's defence against Russia.

The two leaders announced the deal in the garden of Starmer's Downing Street residence, where they also met Ukrainian troops being trained in Britain.

"I'm really proud that this afternoon, we're able to announce an industrial military co-production agreement - the first of its kind so far as Ukraine and the UK are concerned - which will be a massive step forward now in the contribution that we can continue to make," Starmer said.

Speaking alongside Starmer, Zelenskiy said the deal would help strengthen both nations, as he thanked Britain for its support in the war against Russia.

The agreement to share battlefield technology would boost Ukraine’s drone production and link up Britain's defence industry with the technology being developed on the front lines in Ukraine, Starmer's office said in a statement.

The agreement, which covers the next three years, comes after the two countries set out a 100-year partnership to deepen security and cultural ties when Starmer visited Kyiv in January.

In a readout of the meeting between the two leaders, Starmer's office said they agreed that the "coalition of the willing" - a grouping led by Britain and France, and not including the U.S. - should convene virtually in the coming weeks to update members on next steps.

Earlier on Monday, Zelenskiy met King Charles at Windsor Castle where the two shook hands for cameras on what was their third meeting this year and the latest gesture of Charles', and Britain's, support for Ukraine.

The Ukrainian leader also met the speakers of both houses of parliament.

(Reporting by William James and Muvija M in London and Anastasiia Malenko and Pavel Polityuk; Editing by Kevin Liffey, Alex Richardson, Kate Holton and Nia Williams)