Intentionally or not, experts say, Trump is undermining that design. But his actions are not as severe as his rhetoric.

Trump signed an agreement at the July 12 NATO summit in Brussels, for example, that again condemned Russia’s seizure of Crimea and reiterated the alliance’s bedrock mutual defense provision, which says an “attack against one Ally will be regarded as an attack against us all.”

And despite widespread concerns in NATO that Trump would start to remove American troops, he has continued to send regular rotations of U.S. troops to Central Europe, where NATO is reinforcing its defenses.

Trump’s attacks have been “damaging but so far it may not be long-lasting damage,” said Alexander Vershbow, who was NATO’s deputy secretary-general from 2012 to 2016 and is a former U.S. ambassador to Russia.