“What bothers me abroad is, look, the idea that we can go it alone with no alliances for the next 20 or 30 years is a disaster,” Biden, the Democratic front-runner to challenge Trump in next year’s general election, told CNN's Chris Cuomo.

“I come out of a generation where we were trying to be the policemen of the world. We can't go in every place. We need allies,” Biden said. “He is absolutely dissing them. He's embracing thugs. He’s embracing Kim Jong Un, who is a thug. He's embracing Putin, who is a flat dictator.”

Biden also accused Trump of “stiff-arming our friends” on the world stage and “threatening NATO,” the decades-old multinational political and military alliance among 29 North American and European countries.