Joe Biden, US president-elect, has delivered a warning to Boris Johnson not to let Brexit destabilise the Northern Ireland peace process, in a call that suggested the "special relationship" is about to become more complicated.
Biden surprised Downing Street by including Johnson among the first world leaders to receive a post-election phone call, but the diplomatic niceties were accompanied by a firm message on Brexit.
"They talked about the importance of implementing Brexit in such a way that upholds the Good Friday Agreement," said one British official, referring to the peace accord that ended decades of violence in Northern Ireland. "The PM assured the president-elect that would be the case."
Biden has previously described Johnson as "a physical and emotional clone of Donald Trump" and warned there would be no chance of a UK-US trade deal if Brexit undermined the Northern Ireland peace process.
Johnson's determination to press ahead with legislation that would allow ministers to break international law and overrule elements of last year's Brexit treaty that relate to Northern Ireland has alarmed the Biden camp.
The prime minister argued he was legislating to ensure open borders between Northern Ireland and the rest of the UK after Brexit and that this was essential for maintaining stability in the region.
British officials were relieved the "warm" 25-minute call took place so early in Biden's schedule; whatever the protests to the contrary, UK diplomats always seek an early affirmation of bilateral ties with the new US president.
Biden's first call was with Justin Trudeau of Canada. Johnson is thought to have been the second leader to offer his congratulations to the president-elect, although that was not confirmed by the Biden team.
The Biden team instead listed the call with Johnson last in a list of four calls Biden held with the leaders of France, Germany, Ireland and the UK on Tuesday. The countries were listed in alphabetical order.
Biden saluted France as its "oldest ally" while talking to President Emmanuel Macron, and he "praised" German chancellor Angela Merkel's leadership, expressing a desire to strengthen US relations with both countries, according to a readout of the calls from the Biden team.
In his call with Micheál Martin, the Irish taoiseach, Biden also "reaffirmed his support" for the Good Friday Agreement and the peace process in Northern Ireland.
Speaking to Johnson, Biden "reaffirmed his support for the Good Friday Agreement in Northern Ireland", according to Biden's team — a subject missing from the UK readout of the call — and expressed his desire "to strengthen the special relationship and redouble co-operation on issues of mutual concern", highlighting efforts on climate change, Covid-19, economic recovery and democracy.
Downing Street said Johnson and Biden discussed trade — prospects for an early US-UK trade deal seem slim — security co-operation and climate change. Britain is hosting the G7 and the United Nations COP26 climate change summits in 2021.
"They discussed the close and longstanding relationship between our countries and committed to building on this partnership in the years ahead, in areas such as trade and security — including through Nato," Number 10 said.
Meanwhile Johnson shows no signs of backing down on his threat to break international law over Brexit, as he prepares another piece of legislation intended to avoid a hard border between Northern Ireland and the rest of the UK.
Johnson has placed himself on a collision course with the EU and Biden by threatening to overrule parts of Britain's EU withdrawal treaty relating to Northern Ireland.
Downing Street said on Tuesday that the prime minister intended to ask MPs next month to overturn Monday's massive defeat in the House of Lords when peers voted by 433 to 165 to pass an amendment to the controversial internal market bill.
The upper house amendment removed measures that would have allowed ministers to "disapply" parts of the Northern Ireland protocol — intended to maintain an open border in Ireland after Brexit — in breach of international law.
Separately Johnson has indicated he will bring forward a twin piece of contentious legislation — a finance bill — giving ministers control over a post-Brexit tariff regime for goods passing from mainland UK to NI.
The prime minister insists he needs a legal "safety net" in the event that the EU interprets the withdrawal treaty in an "extreme" way that effectively places a hard trade border in the Irish Sea.
But Biden has warned that overriding the delicate Northern Ireland protocol could shift that border to the island of Ireland.
The finance bill, which has to be enacted before the end of the Brexit transition period on December 31, is likely to become the focus of more tension between Downing Street and MPs.
The government wants to ensure that tariffs are only paid on goods travelling from GB to NI "if there is a genuine and substantial risk" of them ending up in the Republic of Ireland. Those "at risk" goods are supposed to be identified by mutual agreement with the EU.
If Johnson agrees a free trade agreement with the EU before the end of the transition period, some of the disagreements will fall away, although Downing Street insisted the prime minister still believed a legal safeguard was needed.
After speaking to Ursula von der Leyen, European Commission president, on Saturday, Johnson said the point of the internal market bill "and indeed the finance bill, is to protect and uphold the Good Friday Agreement and the peace process in Northern Ireland".
Many peers hope that Johnson will avoid a constitutional battle with the House of Lords over the internal market bill. Gavin Barwell, former chief of staff to Tory prime minister Theresa May and now a peer, said: "I think the government would be wise to learn lessons from the size of their defeat last night".
Written by: George Parker and Katrina Manson
© Financial Times