US President Joe Biden and British Prime Minister Rishi Sunak say their countries will partner on advanced technologies, clean energy and critical minerals as they strengthen a historical security alliance.

Biden and Sunak signed the “Atlantic Declaration,” which Sunak described as a first-of-its-kind economic partnership on artificial intelligence and other economic and commercial relations, as the British leader made an official visit to the White House.

The US and Britain’s long-standing military and security partnerships have strengthened amid Russia’s war in Ukraine and China’s more aggressive posture in Asia, but a much-hoped-for free trade agreement has not materialised.

“Our economic partnership is an enormous strength – a source of strength that anchors everything that we do together,” Biden told reporters.

“I know some people have wondered what kind of partner Britain would be after it left the EU,” Sunak said, announcing the new deal.

“I’d say, judge us by our actions.

“We’re as committed to our values as ever, as reliable of an ally as ever, as attractive an investment destination as ever.”

Britain exited the EU on January 31, 2020.

Sunak, who took office in October, has pushed to strengthen trading ties between the US and UK, despite the bleak prospects for a post-Brexit free trade agreement.

Biden will ask Congress to rewrite the Defense Production Act to treat British suppliers with some of the favourable terms afforded domestic suppliers.

Biden and Sunak also launched negotiations on a critical minerals agreement that could allow electric vehicle minerals produced in Britain to count towards tax credits for clean vehicles offered under Biden’s Inflation Reduction Act.

That law’s made-in-America bent has frustrated US allies from London to Seoul, and Biden is holding separate talks on the topic with EU leaders.

The meeting, their fourth in as many months, came as Western officials sought to ascertain whether Russia was responsible for the destruction of the Nova Kakhovka dam, which has displaced thousands of people and caused major economic and environmental damage.

Ukraine and Russia have traded blame for the dam’s destruction.

Pledging support to Ukraine for “years to come”, Sunak said he and Biden hoped to send a strong signal to Russian leader Vladimir Putin that there was no point in waiting for allied support for Ukraine to drop, and encourage Putin to withdraw his forces.

Sunak, who regularly called the US president “Joe” during the trip, joked that he would not create the same imposition on Biden that World War II-era UK prime minister Winston Churchill did by allegedly wandering around the White House residence in the middle of the night as a guest of president Franklin D Roosevelt.

The two leaders last met in Hiroshima, Japan, at the Group of Seven summit last month.

They also met in Belfast in April and in San Diego in March at a trilateral event marking the defence partnership of the US, Australia and Britain.

Thursday’s discussion touched on artificial intelligence safety, Sunak told reporters, saying Britain would host the first summit on the issue this autumn to discuss how the risks of AI can be mitigated through internationally co-ordinated action.

In the absence of a bigger trade deal, Britain has cemented deals with individual states and is hoping to reach other such “targeted agreements”.

Sunak was also expected to try to win Biden’s backing for UK defence minister Ben Wallace’s bid to become the next secretary-general of NATO.

Biden said any new NATO leader needed agreement from all allies.

The British leader visited the US Capitol on Wednesday, where he met with Republican and Democratic congressional leaders.

– AAP