Vice President Joe Biden has opened up about his legacy, his friendship with President Barack Obama, and of course, his views on president-elect Donald Trump.

In a New York Times interview published on Tuesday, Biden said that when it comes to Trump’s foreign policy plans, “it’s like a Rubik’s cube trying to figure this guy out. We have no freakin’ idea what he’s gonna do.”

Biden said that it could be “very ugly” if Trump pursues an isolationist agenda, but he stopped short of attacking the man himself.

“It’s one thing to say: ‘I think the proposal on the following is a serious mistake. I think it’s gonna do the following damage,’” Biden said. “It’s another thing to say, ‘The guy’s a fucking idiot, and he is an egomaniac who’s a whatever.’ ”

Biden also addressed rumors that he’s considering a 2020 presidential run.

“I’ll run,” he said, “if I can walk.”

Still reeling from the death of his son Beau, the veep decided not to run in last year’s election. Earlier this month he admitted that “I regret it every day, but it was the right decision for my family and for me.”

Read more of the interview here.