Donald Trump, who was reportedly talked out of withdrawing the U.S. from NATO when he was in the White House, is still threatening to follow through on the idea should he win re-election, according to Rolling Stone. During his first term, Trump wanted to do away with the alliance part of the alliance, in which an assault on one member nation is considered an attack on all. A former administration official told Rolling Stone that, during his presidency, Trump repeatedly said that he wouldn’t be “starting World War III” to help out countries he deemed insignificant. Now on the campaign trail, he’s once again threatening to pull out of NATO if other members don’t ramp up their military spending. Sources told Rolling Stone that he is considering a “NATO on standby” policy. Former Trump national security adviser John Bolton wrote in his memoir that Trump didn’t understand how NATO’s defense spending requirements worked, recalling he would get annoyed that member nations were supposedly not paying enough. These fears come as Trump has voiced frustration at American military aid to Ukraine.