ATHENS, Greece >> Having warned of the risks of a Trump presidency, President Barack Obama returned Wednesday to a more optimistic vision of the future of the United States, as part of his final international tour while in office.

“American democracy is bigger than any one person,” Obama told an audience in Athens, before he departed for Berlin. “That is why we have a tradition of the outgoing president welcoming the new one — as I did last week.”

But he also acknowledged that such transfers of power were not always easy, and he noted that the diversity of American society made governance a challenge.

“As you may have noticed, the next American president and I could not be more different,” Obama said to a ripple of laughter.

Obama has largely spoken positively about the coming presidency of Donald Trump, saying in a Monday news conference that the president-elect had reassured him that he would remain committed to NATO and that he would keep portions of Obama’s health care law.

On Tuesday, Obama seemed to change tack, warning against what he said were dangerous divisions of race, religion and ethnicity.

“We are going to have to guard against a rise in a crude sort of nationalism or ethnic identity or tribalism that is built around an ‘us’ and a ‘them,’” he said.

On Wednesday, he said that “even if progress follows a winding path — sometimes forward, sometimes back — democracy is still the most effective form of government ever devised by man.”

Obama, making his first visit to the Acropolis, did acknowledge that democracy could be challenging.

“And in multiethnic, multiracial, multicultural societies, like the United States, it can be especially complicated,” he said. “Believe me, I know.”

But he said that globalization and automation, which have created the most prosperous and advanced society in history, were also creating extraordinary anxiety.

“Technology and automation mean that goods can be produced with fewer workers,” he said. “It means jobs and manufacturing can move across borders where wages are lower and rights are less protected.”

Those trends have also created a global elite that seems to live by a different set of rules, such as being able to avoid taxes, Obama said. That kind of inequality breeds resentment, he said, and is among the greatest challenges to modern democracies and to the economic formula that has yielded such benefits.

“It fuels a feeling that globalization only benefits those at the top,” he said, adding: “And if people feel that they are losing control of their future, they will push back. We’ve seen it here in Greece and across Europe. We saw it in the vote in Britain to leave the EU. And now, we’ve seen it in the United States.”

Obama said that remaining a connected world was still crucial but that the “current path of globalization demands a course correction” to ensure that the fruits of those trends were more broadly shared.

Standing in the Stavros Niarchos Foundation Cultural Center, which was bedecked with Greek, U.S. and EU flags, Obama made a fervent pitch for the European Union, which some Greeks have advocated leaving in recent years because of the costs of remaining tied to the euro.

“European integration — the European Union — remains one of the great political and economic achievements of human history,” Obama said. “Today, more than ever, the world needs a Europe that is strong, prosperous and democratic.” And he praised Greece for its efforts to shelter thousands of Syrian refugees.

“Like the woman here in Greece who said of the refugees arriving on these shores, ‘We live under the same sun. We fall in love under the same moon. We are all human. We have to help these people,’” Obama said to sustained applause. “Women like that give me hope.”

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