Still, he estimated that German growth was flat in the second quarter, taking a more optimistic line than many others, who predicted a slight contraction. Besides the geopolitical strains, Germany’s weakness resulted from damp demand from eurozone trading partners and one-time factors including statistical distortions caused by unusually mild weather in the first quarter, he said.

“Up to now, the fallout of the Ukraine crisis has been limited to a general return of uncertainty and a sharp drop in German exports to Russia,” Mr. Brzeski said. “Obviously, a further escalation of the crisis could start to really hurt the economy. This is why strengthening domestic demand, particularly domestic investment, should continue to be a top priority for all policy makers.”

The dispute between the West and Russia over Ukraine has led to tit-for-tat sanctions from the United States and Europe on the one hand and Russia on the other. While Russia’s share of the global economy is small, about 3 percent, it is one of Germany’s 10 largest trading partners, according to the Association of German Chambers of Commerce and Industry, and nearly 300,000 German jobs depend on exports to Russia.

Analysts at Natixis, a French bank, estimated that a 30 percent drop in exports to Russia this year would shave “a modest 0.3 percentage points” from Germany’s economic growth.

Mario Draghi, the president of the European Central Bank, acknowledged last week that the economic tensions from the Ukraine crisis would “have a greater impact on the euro area than they have on other parts of the world.”

The eurozone emerged from recession in the second quarter of 2013 by the most common definition, a simple return to growth. But the bloc has never convincingly broken free of the twin shocks of the global financial crisis and the sovereign debt crisis that shook Spain and Italy with punishingly high borrowing costs and led to bailouts for Cyprus, Greece, Ireland and Portugal.

With governments bound by agreement to hold spending in check, demand is slack, business investment remains weak and more than 18 million people in the currency union remain out of work. In June, a group of prominent economists associated with the Center for Economic Policy Research, a nonprofit organization based in London, argued that the eurozone was, at best, experiencing only a “prolonged pause” in the recession that began in the third quarter of 2011.