UK Foreign Secretary Liz Truss said she discussed the UK’s “cast-iron commitment” to the Good Friday Agreement during a meeting with US politicians.
She said it was “great” meeting a bipartisan US congressional delegation led by senior Democrat Richard Neal, with topics of conversation ranging from the peace treaty to “the importance of free trade” and Russia’s invasion of Ukraine.
It comes amid heightened tensions over the post-Brexit deal on Northern Ireland.
Mr Neal, the head of the powerful ways and means committee in the House of Representatives, also spoke with International Trade Secretary Anne-Marie Trevelyan and Labour leader Sir Keir Starmer on Saturday.
Details of the talks with the Cabinet ministers have been thin, with only tweets as a guide to their discussions.
The visit from the delegation follows a warning from US House Speaker Nancy Pelosi that Congress will not support a free-trade agreement with the UK if the government persists with “deeply concerning” plans to “unilaterally discard” the Northern Ireland Protocol.
Ms Trevelyan said she was “delighted” to welcome the delegation to her department to discuss UK-US trade matters, as well as the situation in Ukraine, but made no explicit mention of post-Brexit tensions.
In a strongly-worded intervention on Thursday, Ms Pelosi urged the UK and the EU to continue negotiations on the post-Brexit trade arrangements to uphold peace.
The latest controversy has been sparked by Ms Truss’s announcement on Tuesday that the UK intends to legislate to override parts of the Brexit withdrawal treaty it struck with the EU.
She told the House of Commons the move is needed to reduce “unnecessary bureaucracy” and to protect the Good Friday Agreement, arguing that the EU’s proposals “would go backward from the situation we have today”.
The dispute over the treaty has created an impasse in efforts to form a devolved government administration in Belfast, with the Democratic Unionist Party (DUP) refusing to join an executive unless its concerns over the situation are addressed.
Ms Pelosi’s intervention was met with scorn from former Brexit minister Lord Frost, who called the statement “ignorant” of the “the realities in Northern Ireland”.
“There is no plan to put in place a physical border,” he told the BBC.
“Nobody has ever suggested that, so I don’t know why she is suggesting that in her statement.”
DUP leader Sir Jeffrey Donaldson also described Ms Pelosi’s contribution as “entirely unhelpful”.
Ms Pelosi is not the only senior figure in Washington to express concern about relations between the UK and the EU in recent days.
Derek Chollet, a senior adviser to US Secretary of State Antony Blinken, said on Friday a “big fight” between the UK and the EU is the “last thing” the US wants.