Donald Trump’s suggestion that he might leave some of Russia’s neighbors hanging in the event of Russian aggression, despite the United States’ obligations as a North Atlantic Treaty Organization member, flies in the face of all modern presidents’ national security strategy, White House spokesman Josh Earnest said Thursday.

“The recognition that NATO is the cornerstone of American national security is a policy that the United States has pursued under every post-WWII president, Democratic or Republican,” Earnest said.