BERLIN (Reuters) - Failure by the next German government to fulfill a pledge to boost military spending to two percent of its economic output will weaken the NATO alliance, a senior U.S. military official said on Monday.

Army secretary Mark Esper told reporters during a visit to U.S. troops in Wiesbaden, Germany, that NATO members had recommitted to meeting the NATO 2-percent target in 2017, and he would take the German government at its word that it would stick to that pledge.

“It’s important for all of our NATO allies to live up to their commitments,” Esper said during a teleconference on Monday. “If not, it weakens the alliance, clearly, and Germany is such a critical member of NATO.”

Esper said Germany had a particularly important role in NATO given its economic strength in Europe and its leadership within NATO. “I take the German government at their word that they’re going to get to the 2 percent and live up to that,” he said.

German Chancellor Angela Merkel’s conservatives and the center-left Social Democrats are locked in negotiations about renewing the coalition government that ruled since 2013.

A negotiating blueprint hammered out by the two political blocs did not mention the NATO target specifically - dodging an issue that continues to divide the parties.

The BDI industry association this month estimated that Germany spent just 1.13 percent of its economic output on the military in 2017, well below NATO’s projection of 1.22 percent due to stronger-than-expected economic growth.

BDI expert Matthias Wachter said the percentage could drop further in coming years if the economy’s expansion outpaced planned increases in military spending.

Esper said NATO’s efforts to reassure Poland and the Baltic States remained a key priority to guard against any Russian “adventurism” given Russia’s actions in Georgia and Ukraine.

“We all wish that Russia was on a different trajectory, but after what we’ve seen in Georgia and Ukraine, we have to hope for the best and prepare for the worst,” he said, referring to the Russian military incursion into Georgia in 2008 and the annexation of Crimea from Ukraine in 2014.