As Donald Trump officially enters office, the German government is still struggling to establish contacts with the new administration and distinguish campaign bluster from actual policy.

U.S. President-elect Donald Trump at the "Make America Great Again" Welcome Celebration concert at the Lincoln Memorial in Washington, D.C.

Angela Merkel has more experience navigating the transition of political power in the United States than perhaps any other European head of government.

As the longest-serving Western leader, Ms. Merkel has built close working relationships with two presidents of different political stripes, George W. Bush and Barack Obama, during her 11-year tenure.

The current changing of the guard in the United States, however, has left the German government uncertain about the future course of trans-Atlantic relations.

There’s no clarity from the new American government about its economic and trade policy. Eric Schweitzer, President, German Chambers of Commerce and Industry

Ms. Merkel has never met and knows very little about the unorthodox man being sworn in as the 45th president on Friday, other than the fact that he views her refugee policy as a “catastrophic mistake.”

The chancellor’s office is currently in the process of organizing a meeting between Ms. Merkel and Donald Trump in Washington. Mr. Trump’s son-in-law and close advisor, Jared Kushner, is viewed as the key interlocutor.

The German government, however, has struggled to establish contacts with Mr. Trump’s team. Decision makers in Berlin have largely been left to read the tea leaves in Mr. Trump’s campaign rhetoric and his recent interviews with the European press.

Instead of expressing his concerns through private diplomatic channels, Mr. Trump has publicly dismissed NATO as “obsolete,” threatened German carmakers with a 35 percent tariff and predicted that other nations would leave the European Union.

Ms. Merkel’s team has given up any pretense that Mr. Trump might become more statesman-like once he enters the Oval Office.

“None of us here believe that anymore,” a source in the chancellor’s circle of advisors told Handelsblatt. “The Americans, and the world, will get the Trump they elected.”

What the Trump presidency means for Germany, however, is still not entirely clear. German exporters, for example, are unsure if Mr. Trump is bluffing about tariffs or if he really plans to follow through with this threat against German automakers.

“There’s no clarity from the new American government about its economic and trade policy,” Eric Schweitzer, president of the German Chambers of Commerce and Industry, told Handelsblatt. That’s poison for innovation, Mr. Schweitzer said.

Ms. Merkel’s foreign policy advisor, Christoph Heusgen, has called for Germany and Europeans to have “strategic patience” with the new U.S. administration.

The new U.S. administration also hasn’t staked out a clear position on the Transatlantic Trade and Investment Partnership, or TTIP, though Mr. Trump railed against other free trade deals such as NAFTA and the Trans-Pacific Partnership on the campaign trail.

“We haven’t heard anything,” said Cecilia Malmström, the E.U. trade commissioner. “Trump hasn’t mentioned the word TTIP once since the election.”

Officials in Berlin are struggling to obtain clear answers from the Trump administration. A federal minister, who declined to be named, told Handelsblatt that he only had the email address of his designated U.S. counterpart.

The foreign ministry’s political director and the head of planning apparently flew to the U.S. shortly after the election, presumably to establish contacts. Peter Wittig, the German ambassador to the United States, met with Mr. Trump’s son-in-law and close advisor, Jared Kushner, before the election.

At the European level, E.U. Council President Donald Tusk spoke with Donald Trump and European Commission President Jean-Claude Juncker spoke with Vice President Mike Pence on the phone. Mr. Juncker described the conversation as constructive.

Ms. Merkel’s foreign policy advisor, Christoph Heusgen, has called for Germany and Europeans to have “strategic patience” with the new U.S. administration, which is largely staffed by people who have little or no government experience.

Mr. Heusgen said his initial conversations with the Trump team gave him the impression that they have little understanding of the European Union and how it operates.

Ms. Merkel’s cabinet is resting its hopes on retired Marine Corps general James Mattis, Mr. Trump’s pick for secretary of defense, as a voice of reason within the new U.S. administration. Mr. Mattis is well connected in Europe and views NATO as an anchor of stability.

German officials also have good relations with Senator Jeff Sessions, Mr. Trump’s pick for attorney general. Though Mr. Sessions is on the hard right of the Republican Party, he was a regular guest at the Germany embassy over the years and his home state of Alabama hosts a Daimler plant.

Contacts between the two governments are expected to intensify in the coming months. Mr. Trump’s nominee for secretary of state, Rex Tillerson, is expected by the German government in Bonn for the G20 foreign ministers meeting on February 16.

The following day, Vice President Mike Pence is set to attend the Munich Security Conference, where he will likely meet Chancellor Angela Merkel for the first time.

There’s concern in Berlin that Mr. Trump could play a spoiler role at the G20, which Germany chairs this year. It’s unclear whether or not Mr. Trump, who wants to slash corporate taxes in the United States, will respect global tax treaties and support the fight against shell companies.

Berlin is already lowering its expectations: “Sometimes in politics the conditions are such that you’ve won a lot when you’ve preserved what exists,” a government official said.

Handelsblatt correspondents Thomas Sigmund, Kirsten Ludowig, Klaus Stratmann, Martin Greive, Mathias Brüggmann and Moritz Koch contributed to this article. To contact: [email protected] .