Washington (CNN) As German Chancellor Angela Merkel prepared to bid President Barack Obama farewell in November, a reporter asked her to describe her sentiments about watching her American partner of eight years be replaced by Donald Trump.

Standing in the German Chancellery on a drizzly Berlin afternoon, the notoriously restrained Merkel -- who became Obama's closest global friend only to see him replaced by a man who lambasted her on the campaign trail -- drew on her stolid pragmatism.

"Out goes the president, and a new one comes in," she said.

On Friday, Merkel presses ahead with the new, arriving in Washington for her first face-to-face encounter with Trump after months of preparation and one postponement due to snow. Analysts and White House officials alike say Friday's sit-down will be Trump's most important meeting with a foreign leader since the Republican businessman took office in January.

The strength of Washington-Berlin ties, which flourished under Obama, will likely come to define Trump's relationship not just with Germany but with Europe -- and the rest of the West. Merkel is the continent's longest-serving and most politically assured leader, rendering her the most visible defender of the Western order at a time when both nationalist and populist movements threaten to upend it.

Differences on trade, immigration

Officials in both capitals said there were few concrete goals for the session beyond establishing a functional working relationship between Trump and Merkel, who differ on areas of trade, immigration and climate change.

Merkel, who spoke to Trump by phone in January, pushed for an in-person meeting in order to begin developing the personal ties that she hopes will lead to effective cooperation down the road, according to a German official familiar with her planning.

"Face-to-face talks are always much better than talking about each other," Merkel told reporters in Munich recently.

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A deft politician with a nearly unmatched ability to forge relationships with unpredictable counterparts, Merkel has watched Trump's campaign speeches and closely monitored his public remarks since taking office, according to someone close to her in Berlin. She's asked visiting world leaders who have met Trump, including Canadian Prime Minister Justin Trudeau, about his temperament and style.

Last month she met Vice President Mike Pence in Munich, where he was delivering the first major foreign policy address of the Trump administration, and laid the groundwork for Friday's meeting.

Aides said they expected Merkel to appeal to Trump's sense of businesslike efficiency in an attempt to win over the new US leader. She's used a workmanlike attitude and droll wit to make inroads with two previous presidents. With George W. Bush, Merkel was able to cooperate on key economic issues, despite Bush's deep unpopularity in Germany. With Obama, she forged a bond so deep and obvious it was parodied on "Saturday Night Live."

Previous insults on the trail

She faces a particular challenge in appealing to Trump, however. Trump has on occasion insulted Merkel in his past public comments, criticizing her decision to allow hundreds of thousands of refugees to enter Germany. That decision was also unpopular in Germany, and Merkel has since said she'll devote funds to sending refugees who weren't granted asylum back to their home countries.

"I like her, but I think it was a mistake. And people make mistakes, but I think it was a very big mistake," Trump told the German newspaper Bild in January, suggesting the move allowed potential terrorists into Europe. That was after he derided Merkel a year earlier, contending she was "ruining Germany" while complaining that she was picked as Time's Person of the Year over him.

And Trump and Merkel's first phone conversation, while cordial, contained some tense moments. The call occurred the day after Trump enacted his controversial travel ban on some foreigners looking to enter the US, and Merkel explained to him the requirements under the Geneva Convention to allow entry to refugees fleeing war. Trump, according to a person familiar with the call, chafed at the lecture.

US officials said the issue of refugees will likely arise in Friday's meeting. But they insisted that any past critical comments on the issue will have little bearing on the budding diplomatic relationship.

"My expectation is that they'll have a very positive, cordial meeting," said one senior administration official last Friday.

Another administration official said that the President hoped to get Merkel's advice for dealing with Russian President Vladimir Putin, who, according to US intelligence, ordered cyber-meddling in last year's presidential election and tried to help Trump.

Merkel up for reelection

Merkel herself faces German voters in September, and many in Berlin fear Moscow may seek to influence the outcome through similar means. As she prepares to go before German voters, Merkel faces a delicate balance in her relationship with Trump, who is deeply unpopular in Germany, but with whom she must partner on key global issues.

"How Chancellor Merkel can maximize her chances in that environment, it's a tightrope walk," said Jeffrey Rathke, deputy director of the Europe program at the Center for Strategic and International Studies in Washington. "She wants -- she needs -- a strong transatlantic relationship (but) doesn't want to be too close to the US administration."

On Friday, Merkel is bringing with her to Washington the chief executives of Siemens and BMW, two of Germany's largest businesses, whom she hopes can help her make a good impression on the business-minded Trump. The two companies employ thousands of American workers, a point that Merkel hopes will come through when the pair get to discussing trade issues -- including Germany's trade surplus, which has rankled members of the Trump administration.

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During their talks, Trump and Merkel will also discuss NATO, the defense alliance that Trump bashed on the campaign trail but has since backed. US officials said Trump would pressure Merkel to increase Germany's defense spending to come in line with NATO's budget requirements for member states.

US officials said that American policy toward the European Union was also likely to arise, with Merkel expected to staunchly defend the bloc as it faces a precarious future. Trump has expressed skepticism about the EU, including supporting Britain's decision to exit it.

Pence's speech at the Munich Security Conference -- in which he vowed support for NATO and reiterated the US call for Russia to abide by a ceasefire in Ukraine -- eased some concerns in Europe about US policy going forward. But the relief among German and European leaders is tenuous given the unpredictability of Trump's policy pronouncements and the apparent disagreements among some of his top advisers.

"There is still lingering doubt about how the US sees European security, and whether the US sees its security and Europe's security as intrinsically linked and inseparable," Rathke said. "And I think that will be a key point that the chancellor will want to discuss and get a better sense of, and where I think the President speaking publicly on that topic would make an enormous impact."