Germany's Angela Merkel was set to visit US President Donald Trump on Friday with no illusions of matching his "special relationship" with France's Emmanuel Macron, but hoping to foster a broader dialogue on trade - one of a batch of tricky topics likely to be addressed.



The cautious Merkel has failed to establish a good personal rapport with the brash Trump, and the mood music of her one-day working visit to the White House would almost certainly contrast sharply with the tactile "bromance" between Trump and Macron.



Yet her trip may prove more productive. Before heading home after a three-day state visit in Washington, Macron acknowledged that, despite his efforts to dissuade Trump from pulling out of the multinational Iran nuclear deal, he remained likely to do so.



The Iran deal, looming US tariffs on European steel and aluminum products, a planned Russian gas pipeline running under the Baltic Sea to Germany, and Berlin's military spending are issues that divide Merkel and Trump and likely to come up at their working lunch.



"The chancellor is pleased about this appointment because she is a convinced Atlanticist," a senior German official said. "It is important to cultivate this relationship."



In Washington, a White House official described Germany as one of the US' closest partners and a steadfast NATO ally, adding, "all of Washington is ready to work with Chancellor Merkel's government."



Ahead of the trip, German officials said they expected US tariffs on European steel and aluminum products to kick in on Tuesday, when an exemption expires. But they said Germany would try to negotiate a broad package including other industries.



"I think the chancellor would prefer a broad dialogue with the Americans. The government is open to extending the package to other duties and trade barriers," one official added.



In Washington, a White House official said the US would press Germany about trade deficits that "pose risks to global economic stability," and "would like to remove barriers... to trade so that we can level the playing field."



"We want to work with Berlin on global unfair trading practices because those are impacting our economies in equal measure," he said.



