Relations between Germany and Russia have been fraught since 2014, when Russia seized Crimea and then destabilized the rest of Ukraine by its not-so-secret promotion of an insurgency in the southeast of the country. Russia also denies interfering in recent elections in the Netherlands and France, with any such plans for the German election this fall probably of particular concern for Ms. Merkel.

Ms. Merkel has led the effort among European leaders to keep Western sanctions in place until the fulfillment of the peace agreements signed in Minsk, Belarus.

One crucial economic matter is building a second branch of the Nord Stream pipeline carrying Russian gas to Europe. The strategy is to bypass Eastern European countries by shipping natural gas under the Black Sea in the south and the Baltic Sea in the north. If completed, the system of subsea pipelines would allow Russia to shut off gas to Eastern European countries during political disputes without disrupting hard-currency earnings from customers in Western Europe.

Germans have been among the staunchest supporters of the plan, while European capitals generally hostile to Moscow are opposed to increasing dependence on Russian gas.

The head of the Russian gas giant Gazprom, Alexei Miller, was quoted in Russian news reports last week as saying that the two sides had agreed on paying for construction costs, with Russia paying about half of the more than $10 billion and five European companies the rest.

The twin issues of Crimea and Ukraine could block any improvement in relations, Ms. Merkel’s spokesman, Steffen Seibert, said before her visit. “These are burdensome circumstances which cannot just be talked away,” he said.

Berlin also has doubts about Russia’s intervention in Syria, particularly its support for President Bashar al-Assad in the face of repeated evidence that he deployed chemical weapons against his civilian population.