President Barack Obama conceded that the United States and other world powers have limited ability to solve the most profound challenges facing the world, while calling for a "course correction" for globalisation to ensure that nations do not retreat into a more sharply divided world.
Mr Obama, in his final speech to the UN General Assembly, acknowledged that the extremist and sectarian violence wreaking havoc in the Middle East and elsewhere "will not be quickly reversed".
Still, he stuck faithfully to his insistence that diplomatic efforts and not military solutions are the key to resolving Syria's civil war and other conflicts.
"If we are honest, we know that no external power is going to be able to force different religious communities or ethnic communities to co-exist for long," Mr Obama said.
"Until basic questions are answered about how communities co-exist, the embers of extremism will continue to burn. Countless human beings will suffer."
In a less-than-subtle jab at Donald Trump, the Republican running to replace him, Mr Obama said: "The world is too small for us to simply be able to build a wall and prevent (extremism) from affecting our own societies."
The president was unabashed in his critique of Russia as he laid out his diagnosis of the world's ills.
Mr Obama's long-standing differences with Russian president Vladimir Putin over his actions in Ukraine have accompanied intense disagreement over Syria's future and a series of failed attempts by Russia and the US to resolve the civil war there together.
"In a world that left the age of empire behind, we see Russia attempting to recover lost glory through force," Mr Obama said.
The tough talk about Russia illustrated how little progress has been made in reconciling the diverging interests among the two powers that has allowed the Syria crisis to continue to fester.
A year ago, Mr Obama stood at the same podium and declared anew that Syrian president Bashar Assad must leave power, while Mr Putin gave a duelling speech warning it would be a mistake to abandon Mr Assad.
In the year since, Moscow's leverage in the conflict has strengthened significantly. Russia's military intervention in Syria has helped bolster Mr Assad's standing without pulling it into the military "quagmire" that Mr Obama had predicted.
Mr Obama sought to use his last appearance before the global body to define how his leadership had put the world on a better trajectory over the last eight years. At the heart of that approach, Mr Obama said, is the notion that the biggest conflicts are best solved when nations cooperate rather than tackle them individually.
It is a theme that Democrat Hillary Clinton has put at the forefront of her campaign for president, casting herself as the natural continuation of Mr Obama's legacy.
In another apparent reference to Mr Trump, Mr Obama bemoaned how terrorist networks had spread their ideology on social media, spurring anger toward "innocent immigrants and Muslims".
Mr Obama lamented that the world has become safer and more prosperous at the same time that nations are struggling with a devastating refugee crisis, terrorism and a breakdown in basic order in the Middle East.
He said governing had become more difficult as people lose faith in public institutions and tensions among nations spiral out of control more rapidly.
"This is the paradox that defines the world today," Mr Obama said. "We must go forward, and not backward."
The president cited his administration's outreach to former adversaries Cuba and Myanmar as key examples of progress, along with global cooperation to cut emissions blamed for global warming.
At the same time, he said he sought not to "whitewash" challenges across the globe, some of which he attributed to deepening anxieties about the profound shifts inflicted by technology and growing international interdependence.
"In order to move forward though, we do have to acknowledge that the existing path to global integration requires a course correction," Mr Obama said.
Mr Obama told world leaders they have to do more to open their hearts to refugees who are desperate for a home.
He said the world is more secure if leaders are prepared to help people in need, but they have to follow through even when the politics are hard.
He said leaders must have the empathy to imagine what it would be like for their families if the unspeakable were to happen.
Seemingly speaking of the US, Mr Obama said there are a lot of nations doing the right thing, but many countries, particularly those blessed with wealth and the benefits of geography, can do more to help.
The UN estimates that there are about bout 21.3 million refugees forced to flee due to armed conflict or persecution.
Countries participating in Mr Obama's summit are announcing individual pledges in line with a US goal of increasing humanitarian aid by three billion dollars (£2.3 billion), doubling resettlement and providing access to jobs and education.
Mr Obama welcomed the pledges of increased assistance.
"In the eyes of innocent men and women and children who through no fault of their own have had to flee everything that they know, everything that they love, we have to have the empathy to see ourselves," Mr Obama said in his address to world leaders.
"We have to imagine what it would be like for our families, for our children, if the unspeakable happened to us."
He said the world will be more secure if nations are prepared to help those in need and urged countries to follow through on their pledges "even when the politics are hard".