British Foreign Minister James Cleverly has told US Secretary of State Antony Blinken that Britain's top priority is to protect the Good Friday Agreement, a government spokesperson has said.
"He ( Mr Cleverly) explained the (Northern Ireland) Protocol is, however, causing real problems in Northern Ireland which we must fix," the spokesperson said in a statement.
Mr Cleverly met Mr Blinken at the UN's General Assembly in New York.
British Prime Minister Liz Truss yesterday said that a post-Brexit UK-US trade deal is unlikely for years.
Meanwhile, US President Joe Biden will tell UK Prime Minister Liz Truss that she must work with the EU to find a negotiated outcome to solve post-Brexit tensions over the Northern Ireland Protocol, the White House has said.
They will hold a delayed meeting in New York today, as Ms Truss attends a United Nations summit.
She declined to discuss the protocol with France's Emmanuel Macron a day earlier, and No 10 did not say if she will raise it with European Commission president Ursula von der Leyen.
But US national security adviser Jake Sullivan made it clear that Mr Biden will discuss it "in some detail" with Ms Truss.
Ms Truss is pushing ahead with her controversial Northern Ireland Protocol Bill, that the EU and other critics say will breach international law by suspending elements of the agreement.
There have also been suggestions she could unilaterally trigger Article 16 of the protocol, to override parts of the agreement brokered as part of the Brexit divorce deal.
Mr Biden and Ms Truss will also meet after a tweet from the president sent 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.
While his criticism was surely intended for a domestic audience, it underlined the differences between the two leaders' stances, just as Ms Truss says she wants to foster closer ties with international allies.
Mr Sullivan told reporters the president "will encourage the UK and the European Union to work out an effective outcome that ensures there is no threat to the fundamental principles of the Good Friday Agreement".
"And he will speak in some detail to her about that," he added.
The adviser said Mr Biden will "communicate his strong view that the Good Friday Agreement - which is the touchstone of peace and stability in Northern Ireland - must be protected.
Additional reporting: PA