BRUSSELS — Russia’s violent closure of the Kerch Strait, the sole shipping lane to a major Ukrainian port city, is undermining German support for Russia’s proposed natural gas pipeline to western Europe, according to the State Department.

“When you have a naked act of aggression like that, I think it resonates in German public opinion,” a senior State Department official told reporters after a meeting of NATO’s council on Black Sea security. “We’ve seen some indications in our recent conversations with German officials that they’ve absorbed that message more plainly after Kerch.”