Allies of Joe Biden have made clear that he expects to see a Brexit trade deal concluded swiftly as he seeks to rebuild a "coalition of the West" to respond to the growing spectre of China.
John Kerry, who has been appointed as Biden's climate envoy, has signalled privately that the new administration wants to see a "positive outcome" from the talks.
It suggests Biden's incoming administration is ratcheting up the pressure on Boris Johnson to strike an agreement as UK and EU officials seek a compromise on the issues of fishing rights and "level playing field" guarantees for business.
While both sides believe a deal could be struck as early as next week, the UK continues to insist it is prepared to walk away if Brussels fails to soften its red lines.
However, in an intervention on Tuesday, Biden reiterated that he did not want to see a "guarded border" on the island of Ireland as a result of no deal.
The UK Government's controversial Internal Market Bill has "no deal" clauses related to Northern Ireland that override the Brexit Withdrawal Agreement with the EU, an agreement that prevents the return of a hard border on the island. A trade deal with Brussels would remove the need for those clauses, which conflict with the conditions of the Brexit Withdrawal Agreement and violate the UK's international commitments.
Although Johnson has reassured the President-elect that he is committed to preventing a hard border, Biden told reporters that "the idea of having a border north and south once again being closed is just not right, we've just got to keep the border open".
A senior EU diplomat warned that, if there was a no deal Brexit, he expected Biden to move to swiftly force Britain back to the negotiating table.
"No deal is more sustainable for the EU than the UK, and don't rule out very heavy pressure on the UK by a Biden administration in the US," the diplomat said.
Speaking to The Telegraph, Tobias Ellwood, the chairman of the Commons defence committee, said Biden was determined to settle the Brexit conundrum as he seeks to shift the West's focus to more pressing global threats.
Ellwood, who has been in touch with Kerry in recent days, added: "They absolutely accept that the referendum took place. They want to see a positive income, and it's in everybody's interest for that to happen. His [Biden's] priority will be to build alliances to meet the growing challenges and threats that this era of instability is now throwing at us.
"That is far better achieved with Britain and the EU working together alongside the US. He wants to rebuild a coalition of the West to inject clearer Western resolve. That is clearly more of a challenge if there is no deal. Politically, it becomes more challenging.
"It is in everyone's interest to conclude a positive trade deal but also to set the foundations of arguably the bigger challenge of matching up to the conundrum of a rising China."
His comments were echoed by Neale Richmond, the European spokesman for Fine Gael, a coalition partner in the Irish Government, who told The Telegraph: "President-elect Biden's opinions on Brexit are well known and he has been vocal on his desire to see a deal between the EU and the UK.
"From an Irish point of view, the President-elect has a long standing commitment to peace on this island dating back to his work as a senator. He has been a frequent visitor to Ireland, proud of his roots, while his own family ancestry is from the Cooley peninsula which is on the border.
"His strong comments on the insistence that there will be no return to a hard border in Ireland are important on two fronts. Firstly, the British Government has very clear obligations to the Withdrawal Agreement that must be met either through removing the offending parts of the Internal Market Bill or concluding a trade deal that makes them moot.
"Failure to meet these responsibilities will no doubt have major impacts not just on EU-UK relations but also US-UK relations, with the prospect of the UK having no trade deal with either of its two largest trading partners come January.
"There is a deal there to be had. It is in everybody's interests to conclude one, particularly the UK, and we should be aware the whole world is watching."
"President-elect Biden's remarks underline again the depth of feeling by the incoming US leadership that Brexit must not lead to a hard border between north and south or damage the Good Friday Agreement. That has also been the consistent position of Ireland and the EU. Ireland and the peace process cannot be used as a chess piece by the Johnson administration and we hope that is clearly understood," said a senior Irish source.
Biden held telephone talks on Monday with senior EU figures including Ursula von der Leyen, the president of the European Commission, which is handling trade negotiations on behalf of the bloc, and Charles Michel, the European Council president.
In a call lasting nearly 20 minutes, Michel thanked Biden for his support over the Internal Market Bill row.