JOE Biden has stressed the importance of reaching an agreement with the EU over post-Brexit legislation on Northern Ireland in his first phone call with the new British prime minister.
The transatlantic relationship could be strained if Liz Truss pushes ahead with the plan to override parts of the Northern Ireland Protocol, with the US president proud of his Irish roots and taking a keen interest in the issue.
Both the Washington administration and powerful Irish-American politicians warned Ms Truss's predecessor that any transatlantic trade deal would be off the table if the UK jeopardised peace in Ireland.
According to the White House's account of the call, the two discussed their "shared commitment to protecting the gains of the Belfast/Good Friday Agreement and the importance of reaching a negotiated agreement with the European Union on the Northern Ireland Protocol".
The situation in Ukraine and the "challenges posed by China, preventing Iran from ever acquiring a nuclear weapon, and securing sustainable and affordable energy resources" were also discussed.
A Downing Street spokeswoman said the pair reflected on the "enduring strength" of the special relationship between the UK and US.
Earlier, Mr Biden was the first world leader to congratulate Ms Truss on her new position.
Just as Ms Truss finished her speech and formally entered Downing Street, the US president tweeted: "Congratulations to Prime Minister Liz Truss.
"I look forward to deepening the special relationship between our countries and working in close cooperation on global challenges, including continued support for Ukraine as it defends itself against Russian aggression."
