US President Joe Biden was set Thursday to warn British Prime Minister Boris Johnson not to imperil peace in Northern Ireland at their first face-to-face meeting.
The pair's encounter ahead of a G7 summit, at the start of the president's first foreign tour, is billed by Downing Street as a chance for the old allies to help shape the post-pandemic world, in areas from climate change to technology and trade.
They will agree a modern version of the 1941 charter signed by their predecessors Winston Churchill and Franklin D. Roosevelt that determined the new world order after World War II.
But while keen to reaffirm the strength of the two countries' "special relationship", Biden has reportedly ordered US diplomats to rebuke Johnson over his handling of Brexit and its effects on peace in Northern Ireland.
The Times said Washington's most senior diplomat in London, Yael Lempert, told Brexit Minister David Frost that the UK government was "'inflaming' tensions in Ireland and Europe with its opposition to checks at ports in the province".
US national security advisor Jake Sullivan insisted the president -- a proud Irish-American with distant family still in Ireland -- would not make "threats or ultimatums" to Johnson.
But he said Biden was "rock solid" in the belief that the 1998 Good Friday Agreement that ended three decades of violence over British rule in Northern Ireland must be protected.
Adding to the pressure on Johnson, EU leaders said they would also bring up the row when they meet at this weekend's G7 summit, as EU member Ireland said it welcomed US support.
- Peace deal -
The row centres on new trading arrangements for Northern Ireland introduced in January after the UK left the European single market and customs union, nearly four years after the divisive Brexit vote.
Under a new protocol for the province, checks are supposed to be carried out on deliveries heading into Northern Ireland from mainland Britain, to prevent goods going into the European single market via neighbouring EU member Ireland.
But pro-British unionist communities say the new rules have driven a wedge between the province and the rest of the UK, increasing the likelihood of reunification with Ireland.
London suspended checks earlier this year because of threats to port staff, and the protocol has been blamed for the worst violence in years in the British-run province.
Talks to resolve the simmering row broke up in London without agreement Wednesday, with Europe threatening retaliatory action, including tariffs, if the new trading arrangements are not implemented.
Johnson's spokesman made no comment to reporters about the US warning, adding only: "Protecting the Belfast Good Friday Agreement is in everyone's interests and that's been our focus and priority throughout our talks with the EU."
- 'The US is back!' -
Biden touched down in England on Wednesday night, announcing "The United States is back!" as he outlined the need for global collaboration to rebuild after Covid-19 and to reset diplomatic ties after the isolationism of the Trump era.
The White House said he will announce a "historic" US donation of half a billion Covid-19 vaccine doses for 92 poorer countries, to "supercharge" the collective fight-back against the global pandemic.
Other G7 countries -- hosts Britain, Canada, France, Germany, Italy and Japan -- will also contribute, and outline a "comprehensive roadmap" to ending the pandemic, a senior administration in Washington added.
As Russia and China also engage in so-called "vaccine diplomacy", and campaigners press for a level playing field on global vaccine distribution, the official denied the US was seeking any quid pro quo.
"This is the right thing to do, it's the smart thing to do, and it is tangible proof that it is going to be the world's democracies who ultimately deliver when it comes to beating the Covid-19 pandemic," he said.
Immediately after his arrival, Biden said he would stress the need for a multilateral approach to tackling global issues at every stop on his week-long trip -- and appease allies baffled and alienated by Donald Trump's approach.
The White House said there was a need to renew commitments to "democratic principles in the face of genuine challenges and authoritarian competition" in the world today.
After the G7 ends on Sunday, Biden will visit Queen Elizabeth II at Windsor Castle and fly to Brussels for summits with the NATO military alliance on Monday and the European Union on Tuesday.
Biden wraps up his tour on Wednesday with what is likely to be a tense meeting with Russian President Vladimir Putin in Geneva.