By Kevin Liptak CNN White House Producer

UNITED NATIONS (CNN) -- President Barack Obama painted a dark picture Tuesday of a world divided between those who want to cooperate with global partners and those who want to retreat into division and isolationism.

"Our societies are filled with uncertainty and unease and strife," Obama said during his final address to the United Nations General Assembly, in remarks that seemed to reflect his view of the United States as well as countries abroad. "Despite enormous progress as people lose trust in institutions, governing becomes more difficult and tensions between nations become more quick to surface."

In pushing back against these global dynamics, Obama took an an indirect jab at Republican presidential challenger Donald Trump, declaring that "a nation ringed by walls would only imprison itself."

Obama acknowledged that voices pressing for globalization had too often ignored trends toward inequality, and assessed that indifference helped lead politics toward "aggressive nationalism" and a "crude populism ... often from the hard right."

He said that the world "cannot dismiss these visions," as they are "powerful," but he rejected them and choices that elevate authoritarianism, strongmen and other forces that harm liberalism.

"I believe that at this moment we all face a choice," Obama said. "We can choose to press forward with a better model of cooperation and integration or we can retreat into a world sharply divided and ultimately in conflict along age-old lines of nation and tribe and race and religion. I want to suggest to you today that we must go forward and not back."

He also defended key policies that have come under attack during the US presidential election, including global trade and immigration.

While he warned that "extremism will continue to be exported overseas," he argued that nations shouldn't isolate themselves by not welcoming outsiders.

"The world is too small for us to simply build a wall and prevent it from affecting our own societies," Obama said.

He also said that the United States and other developed nations must set a better example for emerging democracies.

Citing the pervasive role of money in politics, entrenched party allegiances and a patchwork of voting laws, Obama said it was up to long-established nations to show the way forward.

"Those of us who believe in democracy, we need to speak out forcefully. Because both the facts and history is on our side," Obama said. "We better strive harder to set a better example at home."

And in one of the thorniest issues currently confronting the world -- the civil war in Syria -- Obama said there was a "military component" to addressing it, but continued, "there's no ultimate military victory to be won" and that nations must "continue the hard work of diplomacy."

The President concluded his last UN address with a fatalistic warning on global politics.

"Time and again human beings have believed they finally arrived at a period of enlightenment only to repeat cycles of conflict and suffering. Perhaps that's our fate," Obama said in the final lines of his address.

"We have to remember the choices of individual human beings led to repeated world war," Obama said. "But we have to remember the choices of individual human beings created a United Nations so that a war like that would never happen again."

Individual leaders and nations "can choose to reject those who appeal to our worst impulses and embrace those who appeal to our best," Obama said. "We have shown we can choose a better history."

His speech was a final opportunity to harness the commanding optics of the stately General Assembly hall to bolster his message 49 days before votes are cast for his replacement, in a race as much a referendum on Obama's record as a choice for his successor.

Obama's address also came amid fresh reminders of the destabilizing threats he'll leave behind when he departs office in January. Diplomats gathering in New York this week have contended with terror threats at close range, with a blast injuring dozens in Manhattan as the UN convened nearby, as well as a stabbing plot at a mall in Minnesota and a pipe bomb in New Jersey.

Despite Obama touting his achievements, the array of places where Obama's approach hasn't yielded the outcomes he projected during his first appearance here in 2009 were also unavoidable. Those include closing the Guantanamo Bay naval prison, fully withdrawing US troops from Iraq and Afghanistan and negotiating peace between Israel and the Palestinians -- the last a major topic in his first four UN addresses that was entirely absent during last year's speech.

This year, the President took issue with both sides' actions toward one another.

He criticized Israeli settlements, saying the only path to Mideast peace will come when the two sides reconcile deeply held differences.

Palestinians must "reject incitement and recognize the legitimacy of Israel," Obama said.

But he also said peace won't come until "Israel recognizes it cannot permanently occupy and settle Palestinian land."

Obama plans to meet Israeli Prime Minister Benjamin Netanyahu on Wednesday to "discuss the need for genuine advancement of a two-state solution to the Israeli-Palestinian conflict in the face of deeply troubling trends on the ground," according to White House Press Secretary Josh Earnest.

Other persisting crises -- the emergence of ISIS, a bloody civil war in Syria and Russia's continued incursion into Ukraine -- hadn't yet erupted when Obama entered office but have strained his efforts to foster global stability.

Those intractable problems are largely the focus of Obama's bilateral agenda in New York this week, including during talks with Iraq's Prime Minister Haider al-Abadi Monday to plot a campaign to retake ISIS-held Mosul. He also conferred with Chinese Premier Li Keqiang about North Korea's most recent nuclear test.

"On the one hand, there are enormous positive indicators in our world today in terms of economic growth, standards of living, the ability to forge international cooperation on very difficult issues like climate change," Ben Rhodes, Obama's deputy national security adviser, said last week. "At the same time, there's also a great deal of unease."

Obama was well-received when he arrived at the UN in 2009 and vowed to shift US tactics toward collective action rather than the more unilateral approach of President George W. Bush. Obama himself acknowledged that he arrived with outsized expectations rooted "in a discontent with a status quo that has allowed us to be increasingly defined by our differences, and outpaced by our problems."

In the ensuing seven years, Obama maintained his insistence upon pursing diplomatic resolutions to sticky global disputes, best evidenced in the controversial agreement to loosen sanctions on Iran in exchange for the country reducing its nuclear program.

"We made good on the President's pledge to engage with those with whom we disagree, opening up new, profound opportunities for diplomatic progress," said Samantha Power, Obama's ambassador to the UN since 2013. "I think it's hard to overstate the transformative effect that this approach has had."

For all of those achievements, global unease remains -- some of it connected to American political developments. UN delegates are witnessing the caustic final stretch of the US presidential campaign, which has left foreign allies unsure of their standing come January. Obama has used his UN addresses in the past to confront domestic anxieties, including during his reelection battle with Mitt Romney in 2012 and later when racial tensions prompted protests in Ferguson, Missouri, in 2014.

Last year, as isolationist vows and bombastic rhetoric were fueling Donald Trump's rise, Obama warned against turning inward.

"The increasing skepticism of our international order can be found in the most advanced democracies. We see greater polarization, more frequent gridlock, movements on the far right, and sometimes the left, that insist on stopping the trade that binds our fates to other nations, calling for the building of walls to keep out immigrants," he said a year ago. "The United States is not immune from this."

In the ensuing 12 months, those forces have strengthened, evidenced not only by Trump's clinching of the Republican nomination but also a vote in the United Kingdom to exit the European Union and a resurgence of nationalist parties across Europe.

Still, even as both Trump and Democratic nominee Hillary Clinton also stopped by New York this week to meet with world leaders attending the General Assembly, Obama hopes to achieve a last push for greater cooperation between nations even after he leaves office.

"I think the way the President will approach this is trying to apply what we have done that's worked in the last eight years as a template for how we deal with other crises," Rhodes said ahead of Obama's speech.

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