Facing an escalating nuclear threat from North Korea and the mass flight of minority Muslims from Burma, world leaders are gathering at the United Nations to tackle these and other tough challenges - from the spread of terrorism to a warming planet.
United States President Donald Trump and France's new leader, Emmanuel Macron, will be closely watched as they make their first appearance at the General Assembly. They will be joined by more than 100 heads of state and government, including Zimbabwe's President Robert Mugabe, one of Africa's longest-serving leaders who is said to be bringing a 70-member entourage.
While Trump's speeches and meetings will be closely followed, it will be North Korea, which Secretary-General Antonio Guterres calls "the most dangerous crisis that we face today", that will be most carefully watched. No official event addressing Pyongyang's relentless campaign to develop nuclear weapons capable of hitting the US is on the UN agenda, but it is expected to be the No. 1 issue for most leaders.
Not far behind will be the plight of Burma's Rohingya Muslims, victims of what Guterres calls a campaign of ethnic cleansing that has driven nearly 400,000 to flee to Bangladesh in the past three weeks. The Security Council, in its first statement on Burma in nine years, condemned the violence and called for immediate steps to end it. British Foreign Secretary Boris Johnson was to host a closed meeting on the crisis today, and the Organisation of Islamic Co-operation's contact group on the Rohingyas is scheduled to meet tomorrow.
Guterres said leaders would also be focusing on a third major threat - climate change. The number of natural disasters is on the rise and he pointed to unprecedented weather events in recent weeks from Texas, Florida and the Caribbean to Bangladesh, India, Nepal and Sierra Leone.
While Trump has announced that the US will pull out of the 2015 Paris Climate Agreement, Macron will be hosting a meeting tomorrow to spur its implementation. And a late addition to the hundreds of official meetings and side events during the ministerial week is a high-level session today on the devastation caused by Hurricane Irma.
Several terrorism-related events are on the agenda. Macron is holding a meeting today with leaders of five African nations - Mali, Mauritania, Niger, Burkina Faso and Chad - that are putting together a 5000-strong force to fight the growing threat from extremists in the vast Sahel region.
A side event on Thursday on "Preventing Terrorist Use of the Internet" will be attended by senior representatives of major social media companies. Co-hosts Britain, France and Italy said a global response is needed "to make the online space a hostile environment for terrorists".
Trump has accused Iran of supporting terrorists and is threatening to rip up the 2015 deal to rein in its nuclear programme. With a US decision due in October, ministers from the six parties to the agreement are expected to meet next week. The five others strongly support the deal.
Trump has also been critical of the UN and has promised to cut the US contribution to its budget, which is the largest. So some diplomats were surprised that the US would sponsor an event today on reforming the 193-member world body.
Trump and Guterres will speak, and the US has asked all countries to sign a declaration on UN reforms. More than 100 have added their names, but Russia's UN Ambassador Vassily Nebenzia said on Saturday that "we are not sure we will sign this declaration". He said that while "lots of ideas contained in this document are important and look similar to what the secretary-general proposes", UN reforms should result from negotiations among all countries instead of from "a declaration of like-minded countries".
The Security Council is holding a high-level meeting on Thursday on UN peacekeeping operations, which cost nearly US$8 billion ($10.9b) a year. The US, which pays more than 28 per cent of the peacekeeping budget, is reviewing all the missions in an effort to cut costs and make them more effective.
While there are many side events on other global hotspots from Central African Republic and South Sudan to Libya, Mail and Somalia, the ministerial meeting will also feature sessions on achieving UN goals for 2030 to end extreme poverty and preserve the planet, women's economic empowerment, migration and conflict prevention - a top priority of the secretary-general.