Boris Johnson will try to convince key EU leaders that the UK is developing a workable plan for the Irish border after Brexit, when he meets them in the margins of the United Nations general assembly in New York.
As well as face-to-face talks with Donald Trump – his first meeting with the US president on American soil since becoming prime minister – Mr Johnson will hold discussions with Germany’s Angela Merkel, French president Emmanuel Macron, Irish premier Leo Varadkar and European Council president Donald Tusk.
Flying out to New York on Sunday and returning on Wednesday, he is likely to be in the US when the Supreme Court releases its ruling on the legality of the five-week suspension of parliament, which has been promised early next week.
Mr Johnson’s partner Carrie Symonds is travelling separately to New York for meetings related to her own work on wildlife preservation. Downing Street said no public funds were being spent on her itinerary and she was not attending any official functions as Mr Johnson’s partner, though it was unclear whether the pair would spend time together during the visit.
The prime minister’s talks with Mr Trump are expected to focus on last weekend’s drone and missile attacks on Aramco oil facilities in Saudi Arabia, which will also feature in discussions with Ms Merkel and Mr Macron, meeting as the E3 group of European powers.
The meetings come after a 30-day period for progress on Brexit, floated by Ms Merkel last month, passed without the UK putting forward concrete proposals for a new withdrawal deal.
No Brexit breakthroughs are thought likely to emerge in New York, but Mr Johnson is expected to put more flesh on the bones of proposals to replace the controversial backstop arrangements to keep open the border between Northern Ireland and the republic.
The UK has submitted documents outlining a basis for technical discussions on customs, manufactured goods and sanitary rules, but the so-called “non-papers” do not constitute formal proposals for discussion.
A senior British official said: “This visit gives the prime minister an opportunity to talk at leader level about what some of our proposals are. He has had a positive meeting with the commission president and a warm phone call, but we are under no illusions that there is still an awful lot of work to do.
“The onus is on everybody to work hard to try to find a way through.”
Mr Tusk is also due to meet Mr Varadkar on Monday.
On Friday, the EU rejected a request from the Brexit secretary Stephen Barclay for London to be given until December 2020 to come up with alternative arrangements to remove the need for a backstop keeping either Northern Ireland or the whole UK in a customs union.
EU leaders have instead said they want detailed proposals by the end of September.
UK officials said Mr Johnson will be playing an active role in UN discussions on issues ranging from climate change to biodiversity, the Middle East, sustainable development and girls’ education.
Mr Johnson and Mr Trump are expected to discuss their security assessments of the Aramco attack, which they agreed earlier this week would require “a united diplomatic response” from the international community.
The PM will also meet New Zealand’s Jacinda Ardern and King Abdullah of Jordan for a summit on countering terrorist narratives online, and will hold talks with Indian PM Narendra Modi, Ukrainian president Volodymyr Zelensky, Turkish president Recep Tayyip Erdogan and Egypt’s president Abdel Fattah el-Sisi.