London(CNN) US President-elect Joe Biden has cranked up the pressure on Boris Johnson to strike a post-Brexit trade deal with the European Union, as negotiations between the UK and Brussels enter what could be their final few days.
Speaking with reporters in Delaware, Biden said he had talked to the UK Prime Minister, the Irish Taoiseach and the government of France among others and made clear his opposition to a guarded border between the Republic of Ireland, an EU member state, and Northern Ireland, which, as part of the UK, has left the EU.
The President-elect said the "idea of having the border north and south once again being closed, it's just not right," adding that it's incumbent on every stakeholder to "keep the border open."
The UK left the EU on January 31, and is currently in a transition period which expires on December 31, with or without a formal trade deal in place.
The return of a hard border between the two has always been viewed as a potential consequence of no deal being reached between the UK and the EU, despite an agreement made last year when the first Brexit deal was struck to keep the border open.
Johnson's government exacerbated these concerns over the summer, when it introduced domestic legislation that, by the government's own admission, would breach the treaty Johnson had signed with the EU, breaking international law in a "very specific and limited way."
The Internal Market Bill would allow the British government to effectively ignore parts of the Northern Ireland Protocol in order to keep trade between the four nations of the UK as seamless as possible. However, critics believe that in the event of a no-deal Brexit, this could create the need for customs checks between the Republic of Ireland and Northern Ireland.
Their fear is that any infrastructure on that border would then be at risk of being vandalized or customs officers being attacked, leading to a need for a guarded border. This, many worry, would begin a dangerous slide back to the sectarian violence that claimed more than 3,500 lives over three decades.
American politicians in both parties, most notably former Democratic President Bill Clinton, played a large part in negotiating the 1998 Good Friday Agreement, which bought an end to much of the violence.
Biden has spoken publicly about the matter before, tweeting in September: "We can't allow the Good Friday Agreement that brought peace to Northern Ireland to become a casualty of Brexit. Any trade deal between the U.S. and U.K. must be contingent upon respect for the Agreement and preventing the return of a hard border. Period."
Britons and Europeans who desperately want a deal struck in the next few days are hopeful that this will prove to be a sufficient carrot for Johnson to unlock the talks and avoid a crash-out. Agreeing to a trade deal with the US has always been held up by Brexiteers as a chief benefit of having left the EU. And it's no secret that Johnson is keen to build a good relationship with Biden.
Time is running out though. The Brexit talks have been stuck on the same issues for months. With Johnson due to speak to the President of the EU Commission at some point this week, the hope among those who want a deal, is that Biden's words will nudge Johnson to finally make the necessary concessions.