Rishi Sunak described the US as the UK’s “closest ally” as he met Joe Biden for bilateral talks on the sidelines of the G20 summit in Bali.

The pair’s first full in-person talks, held on Wednesday at a luxury resort hotel on the Indonesian island, came after a missile – initially thought to be Russian-made – fell in Poland and Moscow pounded targets across Ukraine with missiles.

In brief remarks at the top of the meeting, the US president said: “This morning we’ve already met with our fellow Nato and G7 leaders to address Russia’s latest missile strikes against Kyiv and Western Ukraine – it’s merciless.

“I mean it borders on — it’s way over the top.

“At the moment where world leaders meeting here in Bali are seeking progress on world peace, (Russian President Vladimir) Putin’s striking civilian targets – children, and women. I mean, it’s just, It’s almost – in my words, not yours – barbaric.”

In reply, Mr Sunak said: “It’s a great honour to have the opportunity to sit down with you. I think the partnership between our countries is unique and enduring. And of course, it’s bigger than any two individuals. I’m proud to have stewardship of it at the moment.

“And as you said, the United States is our closest ally, biggest trading partner, closest security partner.

“And I’m glad to see that partnership in action doing good whether it’s standing up to – and I agree with your words – barbaric activity by Russia in Ukraine, but also tackling climate change, stabilising the global economy.”

The leaders highlighted that Russia’s invasion of Ukraine is “directly responsible for precipitating global economic issues” in their bilateral meeting, Downing Street said afterwards.

A No 10 spokesperson said: “The leaders agreed on the national and international importance of the strong UK-US relationship, particularly given the challenging economic times the world is currently facing.

“The Prime Minister and President Biden underscored that the actions of President Putin and his regime are directly responsible for precipitating global economic issues including rising inflation. Maintaining international pressure to ensure Putin fails in Ukraine is in everyone’s interest

“The leaders agreed to work together, and with allies, to address the economic consequences of Putin’s brutality. This includes action to protect the most vulnerable in our countries and around the world, and efforts to secure our long-term energy supply.”

The No 10 spokesperson added: “They stressed the importance of likeminded allies providing a counterpoint to authoritarian regimes, including ensuring developing countries can grow in a sustainable way.

“The Prime Minister and President Biden both agreed on the importance of sustained engagement in the Indo-Pacific region and pointed to the AUKUS pact as an example of that. The Prime Minister outlined the UK’s Indo-Pacific priorities, including joining the CPTPP trade bloc.

“The leaders looked forward to working together to take forward cooperation between the UK and the US on areas including trade, defence and upholding the Belfast (Good Friday) Agreement.”

The two leaders and their delegations met in an open-air room, surrounded by a carp pond and tropical plants and shielded from the hot midday sun by a thatched roof.

They have already had plenty of opportunities to speak during the two-day G20 gathering of leaders of the world’s major economies.

Cross-Atlantic relations relations were somewhat strained in recent years amid ongoing UK-EU tensions over post-Brexit arrangements in Northern Ireland.

Mr Biden, the US President with proud Irish heritage, was concerned about the threat to the Northern Ireland peace process.

He recently appeared to publicly criticise Mr Sunak’s predecessor Liz Truss’s doomed economic strategy, in a rare intervention by the US president.

The bilateral meeting came as Donald Trump announced his presidential candidacy for 2024.