World leaders from 136 countries are headed to New York City for the 74th Session of the United Nations General Assembly (23-27 September).
From the climate crisis to the Brexit impasse, including rising tensions in the Middle East, Euronews takes a look at the key issues that will dominate the agenda at the multilateral summit.
About 60 countries will take part in the Climate Action Summit this Monday, just three days after millions of young people took to the streets to demand faster responses to global warming.
That's about just half of the 136 countries attending the UN General Assembly this year.
US President Donald Trump and Brazilian President Jair Bolsonaro, among the world’s only global leaders that publicly question climate science, are not due to take part.
Swedish teen Greta Thunberg will take the podium in the morning following a speech by Secretary-General Antonio Guterres.
Guterres has asked countries to bring "concrete, realistic plans" to enhance commitments made in 2015 in Paris toward the goal of limiting long-term warming to less than 2 degrees Celsius — and ideally 1.5 degrees Celsius — over pre-industrial levels.
These are deemed important to avoid hitting a number of so-called "tipping points," like the melting of polar permafrost, that could trigger irreversible warming and fundamentally alter weather events and ecosystems.
Seventy-five countries are expected to bring enhanced commitments.
But officials have also been careful to manage expectations and say Monday’s summit is also a run-up event to the 2020 UN climate summit that the UK will host in Glasgow.
Still, there is some sense of increased urgency.
The goal of carbon neutrality was considered so radical in 2015 that it was left out of the text of the Paris agreement.
Now, though, it has become a rallying cry for countries like the United Kingdom and France as well as major corporations.
Iran and tensions in the Gulf
After an attack on Saudi oil facilities, which the United States has blamed on Iran, all eyes at the United Nations will be on the recent Gulf tensions.
Iran denies involvement in the attack, which was claimed by Yemen’s Houthi movement, a group aligned with Iran and currently fighting a Saudi-led alliance in Yemen’s civil war.
Hopes at the end of August that Presidents Trump and Rouhani could meet at the United Nations appear to have all but died.
"The meeting between President Trump and President Rouhani is not the number one subject. The priority subject is whether we can restart a de-escalation path with the different actors," French Foreign Minister Jean-Yves Le Drian told reporters on Sunday.
France has led a European effort to try to defuse tensions between Washington and Tehran. But those efforts have stalled, with Iran reducing its commitments to a 2015 nuclear deal with world powers and the United States refusing to ease sanctions that have strangled Iran's economy.
French President Emmanuel Macron is due to meet British Prime Minister Boris Johnson and German Chancellor Angela Merkel, whose countries are also parties to the nuclear deal, on Monday, as well as Trump and Rouhani.
Rouhani said last week he will present the UN with a plan for creating security in the Gulf, without providing further details.
Both Indian Prime Minister Narendra Modi and his Pakistani counterpart Imran Khan will attend the UN General Assembly amid a particularly tense time on the subcontinent.
The Indian leader further strained long-simmering relations with Pakistan last month by revoking the partial autonomy enjoyed by Muslim-majority Kashmir, which both nuclear-armed countries claim.
Modi's move has been met by international criticism.
Pakistan has condemned the crackdown and its Prime Minister Imran Khan warned it would drive more of the world's Muslims into extremism.
The UN Secretary-General is likely to use the opportunity of discussions during the high-level UN General Assembly session to raise the Kashmir issue, his spokesman said last week.
The Venezuelan opposition is planning a series of events on the sidelines of the UN gathering to draw attention to the Venezuelan situation.
With the support of Washington and various Latin American nations, the opposition wants European countries to impose more targeted sanctions on Maduro’s government.
The EU will also be under pressure to cut off financial transactions conducted via European institutions as well as the illicit gold trade, an opposition spokesman said.
Most western nations consider President Nicolas Maduro illegitimate - saying he secured a second term last year via a fraudulent vote.
Opponent Juan Guaido led a failed uprising in April against Maduro, who is accused of human rights violations and has overseen an economic collapse prompting millions to flee the country.
Maduro will not attend the UN General Assembly but said two of his envoys would attend to denounce US sanctions.
UK Prime Minister Boris Johnson, who has vowed to deliver Brexit on October 31 with or without a deal, will meet EU leaders on the sidelines of the United Nations General Assembly including Germany's Angela Merkel and Irish Prime Minister Leo Varadkar.
He will also discuss progress on reaching a Brexit deal with European Council President Donald Tusk.
"I would caution you all not to think that this is going to be the moment," Johnson told reporters on the plane to New York.
"I don't wish to elevate excessively the belief that there will be a New York breakthrough."
Johnson said that while a "great deal" of progress had been made since he took office in July as EU leaders now acknowledged the Withdrawal Agreement reached with his predecessor needed to be changed, there were "clearly still gaps and still difficulties".
Both sides remain split over London's desire to remove the Irish border "backstop" from the divorce deal.