Boris Johnson is to meet with Donald Trump, Emmanuel Macron and Angela Merkel at the UN assembly to discuss Brexit, Iran and the climate crisis.
The Prime Minister arrives in New York on Sunday for the annual General Assembly, where world leaders will also convene for the UN's Climate Action Summit.
Mr Johnson will meet the US president, with whom he is expected to discuss Iran, Afghanistan and the climate crisis - which may be a tetchy subject for Mr Trump who has described it as a "hoax".
His meeting with French President Mr Macron and German Chancellor Mrs Merkel is being billed as an E3 meeting, to discuss the attacks on the Aramco oil facilities in Saudi Arabia.
Though a senior Government official said: "I'm sure Brexit will come up.
"What this gives the PM an opportunity to do is talk to them at leader level about what some of our proposals are.
"At the same time we are under no illusions that there's an awful lot of work to do."
It is likely they will discuss the three "non-papers" the UK has shared with the bloc, focusing on the agrifood zone, customs issues and on manufactured goods.
The PM will also meet European Council president Donald Tusk, as he bids to reach an agreement ahead of the October 31 Brexit deadline.
Mr Johnson will meet his Irish counterpart, Leo Varadkar, following his deputy's warning a "wide gap" remains between the UK and the EU on securing a new deal.
EU chief Jean-Claude Juncker buoyed hopes by insisting "we can have a deal", but Ireland's deputy prime minister Simon Coveney said a "wide gap" remains between Mr Johnson and the bloc.
Other "wider foreign policy" issues such as Iran and Syria will also be discussed, the official said.
Ahead of the assembly, the PM said he would be raising three "crucial issues".
Prime Minister Boris Johnson - In pictures
He said: "First, how Britain can work with our European and American allies on peace and stability in the Middle East.
"Second, how science and new technologies can help the world deal with climate change and the threats to biodiversity.
"And third, how post-Brexit Britain will be a better place to invest in and live in."
The PM's partner, Carrie Symonds, is also expected to attend the General Assembly.
However, the official stressed she was travelling for her own work with environmental group Oceana and not with the PM.
Her attendance will signal she has surmounted her visa difficulties, after she was barred from visiting the US for reasons which remain unclear.
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Other bilaterals anticipated for the PM are with Turkey's President Recep Tayyip Erdogan, Indian PM Narendra Modi, Egypt's President Abdel Fattah el-Sisi, Ukraine's President Volodymyr Zelensky, Jordan's King Abdullah II and UN Secretary-General Antonio Guterres.
Additional reporting by PA.
