Athens, Greece (CNN) The last time President Barack Obama took questions from reporters abroad, he dismissed Donald Trump as an "unqualified" peddler of "wacky ideas," expressing confidence during his September swing through Asia that voters would ultimately reject the candidate who ran so vocally against his own agenda.

Now, as he embarks upon his final scheduled overseas trip as President, Obama faces an altogether different scenario: Trump is his successor, and instead of a cheering farewell tour, he's embarking upon a reassurance mission for deeply shaken foreign allies.

At stops in Greece, Germany and Peru, Obama will be left explaining the US election results to foreign counterparts whose anxieties about Trump he's been fueling for more than a year by denouncing Trump from podiums across the globe. Obama must now convince foreign governments and populations that the future isn't as bleak as he once predicted.

Air Force One touched down at the Eleftherios Venizelos International Airport in Athens just past 3:30 a.m. ET (10:30 a.m. local) on Tuesday. Obama was met with a red carpet and military pageantry before meeting with the Greek President and Prime Minister later in the day.

Speaking from the White House briefing room before he departed, an upbeat Obama insisted that he would deliver a message of confidence in the future of transatlantic ties during his talks this week.

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"There is enormous continuity beneath the day-to-day news that makes us that indispensable nation when it comes to maintaining order and promoting prosperity around the world. That will continue," Obama said, describing Trump as having "expressed a great interest in maintaining our strategic relationships."

In fact, he claimed that the President-elect had voiced a change in viewpoint during their Oval Office meeting last week on a key multinational issue.

"One of the messages I will be able to deliver is his commitment to NATO and the transatlantic alliance," Obama said. "One of the most important functions I can serve at this stage during this trip is to let them know that there is no weakening of resolve when it comes to America's commitment to maintaining a strong and robust NATO relationship and a recognition that those alliances aren't just good for Europe, they're good for the United States. And they're vital for the world."

Aides said Obama would confront the election results directly in public remarks and in private conversations with leaders as the core aspects of his foreign policy legacy now appear in question.

Indeed, with right-wing nationalist movements gaining steam in capitals across Europe and the world, Obama faces the daunting task of plotting a way forward with a liberal alliance that now appears more fractured than ever.

But Obama will also stress his view that Trump must be given every chance to succeed when he assumes office in January, a message Obama voiced in the Rose Garden the day following the election and again during his meeting with Trump in the Oval Office on Thursday.

"This office is bigger than any one person and that's why ensuring a smooth transition is so important," Obama told journalists at the White House.

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That will not be an easy message to relay in Europe, where leaders were worried merely at the bombastic rhetoric on the campaign trail, let alone the prospects of Trump in the White House. The President-elect has repeatedly questioned core transatlantic and transpacific principles, including suggesting the US would no longer provide a defense umbrella for Japan and South Korea as well as expressing skepticism toward NATO.

Trump has vowed to unravel nearly every aspect of Obama's foreign policy, decrying what he says are bad trade deals, leaving pending agreements with Pacific nations and the European Union virtually dead. And he's promised to scrap key multilateral accords that formed large parts of Obama's foreign agenda, including a deal reached in Paris last year to reduce global carbon emissions and the pact with Iran to curtail its nuclear ambitions.

"The whole trip was designed to give Europe a boost of self-confidence because Europe was increasingly worried about the nature of the US presidential campaign, the tone and tenor coming from then-candidate Donald Trump," said Heather Conley, senior vice president for Europe at the Center for Strategic and International Studies in Washington.

"Now the President has the unenviable task of ... explaining what Europeans are now coining the 'Trump effect,'" Conley went on, noting the heavy slate of elections and referenda across Europe in the coming year that liberal leaders worry now tilt toward nationalist views in the wake of Trump's victory.

"They are very worried, because the same populist, nationalist expressions, whether that's on immigration, whether that is on free trade, have certainly running very strong political currents within Europe," she said.

At his first stop in Athens, Obama plans to tour the Parthenon and meet with Greece's left-leaning Prime Minister as the country continues to work through its debt crisis. The pair are also likely to discuss the ongoing refugee crisis, which has resulted in massive waves of migrants fleeing Syria's civil war arriving on Greece's shores.

Obama also plans to deliver a major address about democracy, using its ancient birthplace to argue for the enduring values of open and free societies. Aides said he'll confront last week's election results directly, as well as the vote in the United Kingdom to withdraw from the European Union, linking the two as evidence that the benefits of globalization haven't yet reached everyone.

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But he'll also provide a rebuttal against arguments for a more walled-off continent, insisting Europe works better as a joint power.

"I believe that European integration is one of the greatest political and economic achievements of modern times, with benefits for EU members, the United States and the entire world," Obama said in an interview with the Athens newspaper Kathimerini before he arrived Tuesday. "Europe is our largest economic partner, and we have a profound economic interest in a Europe that is stable and growing."

In Germany, Obama huddles with Chancellor Angela Merkel, whom he described during Monday's news conference as "probably ... my closest international partner these past eight years."

In the aftermath of Trump's win, Merkel's leadership role in the West has suddenly intensified, leaving her as the most stalwart voice for the type of open and globalized society Obama has backed after he leaves office.

He'll also meet with the leaders of the United Kingdom, France and Italy, and "signal our solidarity with our closest allies and express our support for a strong, integrated, and united Europe."

Photos: World reacts to Trump victory Slovenians toast Donald Trump's victory in Sevnica, the hometown of Trump's wife, Melania, during a broadcast of his acceptance speech on Wednesday, November 9. Trump defeated Democratic presidential nominee Hillary Clinton and will become the 45th president of the United States. Hide Caption 1 of 19 Photos: World reacts to Trump victory The U.S. dollar exchange rate is seen on the board of a bank in Mexico City on November 9. The dollar tumbled against the yen and euro while the Mexican peso fell off a cliff as polling results pointed to a strong showing by Trump. Hide Caption 2 of 19 Photos: World reacts to Trump victory Taxi driver Uljan Kolgjegja holds a flare as he celebrates Trump's victory in Tirana, Albania, on November 9. Hide Caption 3 of 19 Photos: World reacts to Trump victory Bethany Hindmarsh, an environmental activist attending the COP22 Climate Conference in Marrakesh, Morocco, reacts during a protest against Trump on November 9. News of Trump's win has alarmed environmentalists and climate scientists concerned that a Trump presidency could mean the United States pulls out of an international climate deal. Hide Caption 4 of 19 Photos: World reacts to Trump victory Vladimir Zhirinovsky, leader of the Liberal Democratic Party of Russia, left, toasts in front of a TV screening Trump's acceptance speech on November 9. Hide Caption 5 of 19 Photos: World reacts to Trump victory A stock trader at ETX Capital in London gestures to a screen showing the S&P 500 Index on November 9. Global stock markets dropped as Trump's victory became more likely on Election Day. Hide Caption 6 of 19 Photos: World reacts to Trump victory An expatriate Democratic supporter weeps in a restaurant in Phnom Penh, Cambodia, as the election is called in Trump's favor on November 9. Hide Caption 7 of 19 Photos: World reacts to Trump victory Iraqi troops view Trump's acceptance speech in a house in Arbid, on the outskirts of Mosul, Iraq, on November 9. Iraqi Prime Minister Haider al-Abadi congratulated Trump on his win and said he hoped for continued support in the war on ISIS. Hide Caption 8 of 19 Photos: World reacts to Trump victory People react to Trump's victory at the US Embassy in Brussels, Belgium, on November 9. Hide Caption 9 of 19 Photos: World reacts to Trump victory Clinton supporters watch the incoming results at a cafe in Beijing on November 9. Hide Caption 10 of 19 Photos: World reacts to Trump victory A man reads a newspaper proclaiming Trump's victory in Guatemala City, Guatemala, on November 9. Hide Caption 11 of 19 Photos: World reacts to Trump victory People attending an election event in The Hague, Netherlands, react as Trump is declared the winner on November 9. Hide Caption 12 of 19 Photos: World reacts to Trump victory Debris burns in the street during a protest that took place in Oakland, California, after news of Trump's victory. Hide Caption 13 of 19 Photos: World reacts to Trump victory A stock ticker at the Athens Stock Exchange scrolls above a TV screen showing Trump on November 9. Hide Caption 14 of 19 Photos: World reacts to Trump victory People celebrate Trump's win during a victory party at the New York Hilton Midtown Hotel. Hide Caption 15 of 19 Photos: World reacts to Trump victory Two men in Gaza watch coverage of the election on November 9. Hide Caption 16 of 19 Photos: World reacts to Trump victory A trader from ETX Capital reacts in London following the election result. Hide Caption 17 of 19 Photos: World reacts to Trump victory Trump and Clinton supporters clash in New York's Times Square after Trump's victory was declared on November 9. Hide Caption 18 of 19 Photos: World reacts to Trump victory Protesters from Avaaz, a global civic movement, display a sign protesting bigotry outside the White House on Tuesday, November 8. Hide Caption 19 of 19

Merkel finds herself in a stronger position than other US allies in Europe, including France's Francois Hollande, who is deeply unpopular and faces powerful right-wing forces; Italy's Matteo Renzi, who has expended political capital on proposed constitutional reforms that face a referendum vote next month; and the United Kingdom's Theresa May, who is occupied with navigating Britain's exit from the EU.

But even Merkel is facing a backlash from the right over her policy on refugees. There's little expectation that Trump will provide her the same political backing Obama has as she attempts to map Europe's future.

"We must adjust to the fact that US foreign policy will be less predictable, at least for a considerable time," German Foreign Minister Frank-Walter Steinmeier told Der Spiegel this week. "It is to be hoped that in government, not everything is eaten so hot as it was cooked in the election campaign. But the expectations that have been aroused in the American population are huge."

Obama ends his swing in Peru for a meeting of Pacific leaders, his final attempt to cement his eastward shift in foreign policy focus, even as a centerpiece of that plan -- the massive Trans-Pacific Partnership trade deal -- appears dead.

He'll meet for a final time with China's President Xi Jinping as ties between Washington and Beijing enter a deeply uncertain phase. Trump has threatened a more pugilistic approach, vowing to brand China a currency manipulator during his first 100 days in office.