National Security Adviser John Bolton on Sunday explained that President Donald Trump was forgoing "months and months of preparation" for his meeting with Kim Jong-un because it would interfere with the U.S. president's innate ability to "size up" the North Korea leader.

During an interview on ABC's This Week, host Martha Raddatz pointed out that the outcome of most meetings between world leaders were predetermined by prior negotiations.

"He's sees the chance of a breakthrough but I don't think he has stars in his eyes," Bolton said of Trump. "I think one advantage of having this meeting between President Trump and Kim Jong-un so soon, in effect, without months and months and months of preparation is that President Trump will be able to size Kim Jong-un up and see whether the commitment is real."

"It's the reason why the president is both optimistic but realistic at the same time," he concluded.