Joe Biden is set to warn Boris Johnson and the EU not to endanger the Northern Ireland peace process, his national security adviser has said.
The US President has “very deep” concerns that a trade row between the UK and EU could “imperil” the issue, Jake Sullivan warned.
Mr Biden will tell leaders at this weekend’s G7 Summit, in which he left America on Wednesday (9 June) to attend, that gains made since the Good Friday Agreement must be preserved.
The UK and EU are currently at loggerheads over checks in the Irish Sea following Brexit.
There are fears that no compromise could result in violence in Northern Ireland.
Mr Sullivan said the president believes the post-Brexit Northern Ireland Protocol is “critical” to ensuring that the future of the Good Friday Agreement is protected.
Gains of Good Friday Agreement ‘must be protected’
The adviser told the BBC that both sides must continue with negotiations, adding: “But whatever way they find to proceed must, at its core, fundamentally protect the gains of the Good Friday Agreement and not imperil that.
“And that is the message that President Biden will send when he is in Cornwall.”
Mr Sullivan declined to say whether a failure to alleviate the Northern Ireland concerns could jeopardise a transatlantic trade deal, but added that “our concern runs very deep on the Northern Ireland issue”.
In his first overseas trip as US president, Mr Biden and his wife Jill will kick off the eight-day trip to Europe by meeting US personnel stationed at the base in Suffolk.
The president will then have face-to-face talks with the Prime Minister on Thursday in Cornwall, with the summit beginning in Carbis Bay the following day.
Having succeeded Mr Trump after his single fractious term in the White House, Mr Biden said the trip is about “realising America’s renewed commitment to our allies and partners” in an article for the Washington Post.
Boris Johnson hopes for US trade deal
Mr Biden also said he would meet the Prime Minister to “affirm the special relationship between our nations”.
However, this week it emerged Mr Johnson is not a fan of the expression, after an American magazine reported he told aides he does not like the seemingly “needy and weak” term.
Downing Street said he “prefers not to use the phrase” and is instead intent on fostering a “close relationship” with Washington.
Part of that, Mr Johnson hopes, is a trade deal with the US. However, the national security adviser’s remarks were the latest in a string of warnings about Brexit’s impact on Northern Ireland.
The Prime Minister plans to use the summit of leading economies to urge the members – also including Canada, Japan, France, Germany and Italy – to “defeat” Covid-19 by helping to vaccinate the world by the end of next year.
After the summit ends, the president and first lady will meet the Queen at Windsor Castle.
Mr Biden will then depart for Brussels and later Geneva in Switzerland.