After two years of pandemic restrictions and video addresses, the UN General Assembly is again asking leaders to come in person if they wish to speak -- with a sole exception made for Ukrainian President Volodymyr Zelensky.
But the death of Queen Elizabeth II disrupted the summit anew. President Joe Biden of the United States, by tradition the second speaker on the first day, will instead speak on Wednesday.
The first day will feature French President Emmanuel Macron and German Chancellor Olaf Scholz, the leaders of the two largest economies of the European Union, which has mobilized to impose tough sanctions over Russia's invasion of Ukraine.
"This year, Ukraine will be very high on the agenda. It will be unavoidable," top EU diplomat Josep Borrell told reporters in New York.
"There are many other problems, we know. But the war in Ukraine has been sending shock waves around the world."
German Foreign Minister Annalena Baerbock vowed to support countries hardest hit by the fallout from the war as she headed to the General Assembly on Tuesday.
"The brutality of Russia's war of aggression and its threat to the peace order in Europe have not blinded us to the fact that its dramatic effects are also clearly being felt in many other regions of the world," Baerbock said.
But UN Secretary-General Antonio Guterres has been urging leaders not to forget other priorities such as education, the topic of a special summit on Monday.
"Education is in a deep crisis. Instead of being the great enabler, education is fast becoming the great divide," Guterres told the summit.
He warned that the Covid-19 pandemic has had a devastating impact on learning, with poor students lacking technology at a particular disadvantage, and conflicts further disrupting schools.
In a report earlier this month, the UN Development Programme said Covid has set back humanity's progress by five years.
With the Ukraine war leading to a global grain crisis, hunger could be another major issue on the agenda. On Tuesday, more than 200 NGOs called for urgent action from leaders gathered for the General Assembly to "end the spiralling global hunger crisis."
"Around the world, 50 million people are on the brink of starvation in 45 countries," they said, adding that as many as 19,700 people are estimated to be dying of hunger every day, which translates to one person every four seconds.
- Talks between rivals -
In the type of last-minute diplomacy common at previous UN sessions, US Secretary of State Antony Blinken convened a first meeting of the foreign ministers of Azerbaijan and Armenia since a flare-up in fighting.
"Strong, sustainable diplomatic engagement is the best path for everyone," Blinken told them.
Russian Foreign Minister Sergei Lavrov was visiting despite a hostile reaction from the United States.
He met Monday with his French counterpart, Catherine Colonna, who urged Russia to allow a security zone outside the Zaporizhzhia nuclear plant, whose occupation by Moscow has raised mounting concerns.
Also high on the agenda for the UN week will be Iran, whose hardline president, Ebrahim Raisi, is traveling to the General Assembly for the first time and will meet Tuesday with French President Emmanuel Macron.
In a US television interview ahead of his arrival, Raisi said that Iran wanted "guarantees" before returning to a nuclear deal that former president Donald Trump trashed in 2018.
"We cannot trust the Americans because of the behavior that we have already seen from them. That is why if there is no guarantee, there is no trust," he told CBS News' "60 Minutes" program.
Biden supports a return to the 2015 agreement, under which Iran drastically scaled back nuclear work in return for promises of sanctions relief.
But the Biden administration says it is impossible in the US system to promise what a future president would do.
"There is no better offer for Iran," Colonna said ahead of the meeting with Macron.
"It's up to them to make a decision," she said.
Raisi can expect to be dogged by protests during his visit including by exile groups that have called for his arrest over mass executions of opponents a decade after the 1979 Islamic revolution.