WASHINGTON — (CNN) President Barack Obama took to the most prominent international stage Tuesday to deliver a stark warning to American voters of the dire global consequences they face should they embrace isolationism and ultra-nationalism in November.

Never mentioning Republican presidential nominee Donald Trump by name, the President’s final address to the United Nations General Assembly was at heart an impassioned rebuke of the GOP candidate’s policies on trade, immigration and multiculturalism — and a defense of liberalism and tolerance — delivered 49 days before votes are cast for his replacement.

He painted a dark picture of the future awaiting Americans, and the world, if the forces of “aggressive nationalism” or “crude populism” win out.

And he specifically inveighed against building a wall — a centerpiece of Trump’s proposal on border security.

“A nation ringed by walls would only imprison itself,” Obama declared to the assembled representatives of the UN’s member states.

Gone were Obama’s idealistic appeals to bring about a world free of nuclear weapons and an agenda focused on peace, as were his previous UN addresses.

The “hope and change” of his argument as a presidential candidate himself was also replaced by exhortations against a future filled with chaos.

“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 suggested.

“We have to remember the choices of individual human beings led to repeated world war,” Obama said.

“Each of us as leaders, each nation can choose to reject those who appeal to our worst impulses and embrace those who appeal to our best. For we have shown that we can choose a better history.”

He pointed to growing divisions and discontent at home that challenge those decisions, and noted that the shortcomings of globalization had created “an uncertainty and unease and strife” that required acknowledgement, but not turning inward.

“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.”

It was Obama’s eighth and final address to the UN body, which enthusiastically welcomed him in 2009 after he moved to reverse the unilateral approach of his predecessor George W. Bush.

In his speech that year, Obama vowed to work within international bodies to confront the world’s crises while pushing an agenda combating climate change and nuclear non-proliferation.

But in the intervening years, the harsh realities of diplomacy settled in, both for Obama and the UN.

The organization’s inability to stem suffering in Syria and Ukraine laid bare the continued struggles to combat breaches of international law, while Obama’s own work toward combating violent extremists has failed to stop terrorist groups from committing atrocities.

Obama’s address Tuesday reflected those realities. He drew titters from the collection of world leaders and diplomats in the high-ceilinged General Assembly hall when he noted that “at times both America’s adversaries and some of our allies believe that all problems were either caused by Washington or could be solved by Washington. And perhaps too many in Washington believe that, as well.”

He made scant mention of individual world flash points, choosing instead to offer a more thematic recap of his foreign agenda.

“The world is by many measures less violent and more prosperous than ever before. And yet our societies are filled with uncertainty and unease and strife,” Obama said.

“Despite enormous progress, as people lose trust in institutions, governing becomes more difficult and tensions between nations become more quick to surface.”

Obama continued his tradition at the UN of acknowledging areas where the US has fallen short in its practice of democracy, saying his country 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.”

Obama used his own efforts to help revive a stalled economy as an example of US leadership during his tenure, saying other countries would be wise to follow his lead of going after corruption and unfair tax policies.

He also cited the deal with Iran to curtain its nuclear program, and reopening of ties with Cuba and Myanmar, as examples of a successful global approach.

But 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.

That includes his inability to negotiate peace between Israel and the Palestinians — 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.

Another persisting crisis — Russia’s continued incursion into Ukraine — also drew Obama’s attention Tuesday.

“In a world that left the age of empire behind, we see Russia attempting to recover lost glory through force,” Obama said.

“If Russia continues to interfere in the affairs of its neighbors, it may be popular at home. It may fuel nationalist fervor for a time. Over time, it’s also going to diminish its stature and make its borders less secure.”

Indeed, many of his harshest warnings were aimed at global government practices that damage democracy and liberalism and called for the rejection of strongmen, authoritarian and tribalism.

“There appears to be growing contest between authoritarianism and liberalism right now,” he told the assembled leaders. “And I want everybody to understand, I am not neutral in that contest.”