The US president told the PM that the UK remains 'our closest ally in the world', ITV News Deputy Political Editor Anushka Asthana reports
On Wednesday, the US president insisted the UK remains “our closest ally in the world” while Ms Truss sought to reassure her counterpart, by telling him she would be explaining how the Good Friday Agreement would be upheld.
In opening remarks at the top of their meeting, Mr Biden told Ms Truss: “We are both committed to protecting the Good Friday Agreement of Northern Ireland.
“And I’m looking forward to hearing what’s on your mind.”
He congratulated her on becoming prime minister, adding: “I look forward to working closely with you. You’re our closest ally in the world and there’s a lot we can continue to do together.”
In response, Ms Truss told Mr Biden the UK and US are “steadfast allies” as she thanked him for his support, following the death of Queen Elizabeth II.
“Of course I’m looking forward to discussing the Belfast Good Friday Agreement and how we make sure that’s upheld into the future,” she added.
Mr Biden told reporters that the range of topics he planned to discuss with Ms Truss included Ukraine’s defence against Russian President Vladimir Putin’s invasion, China, and preventing Iran from obtaining nuclear weapons.
“We also want to talk about energy, which understandably is of significant consequence to all of Europe and the United Kingdom in particular,” he added.
Speaking to ITV News ahead of the first talks, the British ambassador to Washington, Dame Karen Pierce, said she thought Ms Truss and Mr Biden will "get on well" as they both "like talking about politics".
"They like talking about possibilities. Both of them are optimistic about the future. Both of them are good problem solvers," she said.
"There's a lot to talk about on Russia [and] Ukraine and sustaining support for Ukraine.
"And we have admired American leadership on that and they have been very complimentary about British leadership. I know they'll want to talk about economic security and I would expect issues like energy to be on the agenda as well."
The British ambassador to the US, Dame Karen Pierce, told ITV News that she believes the relationship between the UK and US is 'as strong as it ever has been'.
Meanwhile, US national security adviser Jake Sullivan made it clear Mr Biden would discuss the Northern Ireland protocol “in some detail” with Ms Truss.
He told reporters that Mr Biden “will encourage the UK and the European Union (EU) to work out an effective outcome that ensures there is no threat to the fundamental principles of the Good Friday Agreement”.
The meeting between the two leaders came shortly after Mr Biden sent a tweet - just as the PM was discussing her economic policy - which said he was “sick and tired of trickle-down economics”.
“It has never worked,” he said.
However, the prime minister’s official spokesman said it was “ludicrous” to suggest Mr Biden was criticising UK policy, arguing each country is facing different economic challenges.
Earlier on Wednesday, Ms Truss held discussions with EU chief Ursula von der Leyen about the post-Brexit agreement and the prevention of a hard border developing between Belfast and Dublin.
The prime minister is pushing ahead with the controversial Northern Ireland Protocol Bill, which the EU and other critics say will breach international law by suspending elements of the agreement.
Suggestions have also been levelled that Ms Truss could unilaterally trigger Article 16 of the protocol, to override parts of the agreement brokered as part of the Brexit divorce deal.