Kim Hjelmgaard

USA TODAY

BERLIN — Donald Trump and Angela Merkel couldn't be more different in political experience, world views and temperament.

They'll find out if they can find any common ground on Friday, when the new U.S. president hosts the long-serving German leader at the White House. They had planned to get together Tuesday but the meeting was postponed because of an expected snowstorm in Washington, D.C.

In personality, Merkel's calm, detailed-oriented leadership for 11 years is in sharp contrast to political neophyte Trump's spontaneity and provocative comments. On policy, they diverge over immigration, defense spending, the European Union and global trade.

"To say that their relationship has been rocky from the start may be the euphemism of the year," said Michael Bröning, director of the foreign policy unit at Friedrich Ebert Stiftung, a Berlin think tank affiliated with Germany’s Social Democratic Party, a center-left opposition group that is part of Merkel's ruling coalition. "They criticized each other before the presidential transition, during it, after it, and they keep on doing it on a regular basis."

"Merkel and Trump really are the polar opposite of each other on so many levels," he said.

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Trump has accused the leader of Europe's most powerful country of "ruining Germany" because of lenient asylum policies that allowed in more than 1 million migrants since 2015. For her part, Merkel has scolded Trump for ordering a temporary ban on immigrants from seven — and subsequently six — Muslim-majority countries, as well as all refugees. She also has publicly questioned his "America first" rhetoric.

Part of the reason for the trip is so that Merkel and Trump can compare notes ahead of the German-hosted Group of 20 economic summit that takes place in Hamburg in July.

Their meeting takes place amid deep unease in Germany and across Europe over how Trump will handle a trans-Atlantic relationship that has been a bastion of stability for decades.

Trump advocates a protectionist stance on trade, trashed the European Union — of which Germany is a strong advocate — and threatened to withdraw support for NATO unless more members of the 28-nation military alliance boost spending levels to 2% of GDP.

Germany, which spends only 1.2% of GDP on defense despite its wealth, has no plan to meet the 2% goal because a stronger military is not a priority for Germans still haunted by the horrors of World War II.

Merkel does not have to make nice to Trump when only 7% of Germans approve of him, according to a poll by Allensbach, a research institute.

Even so, "it's important that Merkel and Trump get to know each other personally," said Peter Beyer, a German politician from Merkel's ruling Christian Democratic Union party. "I am pretty sure there won't be a screaming match."

"Merkel is pragmatic and understands her role quite well," Beyer said. "She's not emotional. And I think it's going to help in these new times when we have this new president who we all agree is a very special individual."

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The White House said it expects a "robust discussion" between the two leaders on security, Russia, EU, trade and Trump's push for NATO members to spend 2% of their GDP on defense.

Rainer Arnold, a German parliamentarian who is the opposition party's senior spokesman on defense policy, said he expects Merkel to "confidently express German and European views" on common security threats and strong economic links, and no change on defense spending.

Brigitte Zypries, Germany’s economy minister, said in an interview Friday with German media that her country may sue the U.S. before the World Trade Organization if Trump goes ahead with a planned "border tax" on imported goods. "It wouldn’t be the first time that Mr. Trump has lost in the courts," she told public broadcaster Deutschlandfunk.

Merkel is running for re-election in September, and recent polls show that for the first time she looks vulnerable to defeat by Social Democratic Party leader Martin Schulz, a virulent critic of Trump.

While Merkel is unlikely to seek concessions from Trump for Germans back home, the election adds another complication to her visit, said think tank analyst Bröning.

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"The preconditions for a good relationship are not really there considering that Trump criticized Merkel quite a bit on the campaign trail," said Sudha David-Wilp, a senior fellow at the Berlin office of the German Marshall Fund, a think tank headquartered in Washington. "But there is still obviously potential for a good relationship because Trump has also expressed his admiration for Merkel because she is a person who has been in power for quite a long time."