U.S. Democratic presidential front-runner Bernie Sanders reaffirmed his resolve to meet with North Korean leader Kim Jong-un if he were to assume office.

In an interview with CBS' "60 Minutes" on Sunday, Sanders said meeting with people who are antagonistic is "not a bad thing" for him.

Without specifying which of U.S. President Donald Trump's past summits with Kim, Sanders said it was unfortunate that Trump went into the meeting "unprepared."

Sanders added that the meeting, while a photo opportunity, didn't have the kind of diplomatic work necessary to make it a success.

Sanders' step-by-step approach towards North Korea, which has been more open and flexible compared to that of his Democratic rivals, is also in contrast to Trump's "top-down" and "big deal" approach based on his personal relationship with Kim.

Sanders is decisively in the lead of the Democratic Party's primary race after votes in Iowa, New Hampshire and Nevada.