President Trump has agreed to meet with North Korean leader Kim Jong Un – a stunning shift in the relationship between the two countries. The summit would mark the first time a sitting U.S. president and a leader of North Korea have ever met, and according to South Korea's national security adviser, denuclearization of the North is on the table.

Nicholas Burns served as the U.S. ambassador to NATO and undersecretary of state for political affairs under President George W. Bush. He told "CBS This Morning" that while diplomacy is a "positive" given escalating tensions between Washington and Pyongyang, the top-level meeting remains a "huge gamble" for the United States.

"We were on a collision course with North Korea. There was a possibility of a war with unpredictable and potentially catastrophic consequences. So if there's going to be a period of the next two or three or four months of diplomacy, I think that's positive," Burns said.

The risks, according to Burns, lie in the North's history of violating their agreements – as they did under Presidents Clinton and Bush – and in their strengthened position in terms of nuclear capability.

Kim Jong Un is "just about, maybe, on the verge of having the capacity to achieve a nuclear weapon that could hit the United States," Burns said. "He wants legitimacy, he wants sanctions relief. I think he'll be open, maybe, to negotiating some transparency about his nuclear weapons. I don't think he'll give them up. So for the president, our president, this is going to be as difficult as it gets and a major gamble."

Adding to the potential risks is the lack of government experts who understand North Korea, and a "dismantled" State Department.

"You have no American ambassador in Seoul [South Korea]. No North Korean expert. Our greatest expert just left last week. So you don't have a bench, you don't have the talent you would normally have because President Trump has forsaken the State Department," Burns said.

And if the summit fails? Burns says there's "nowhere else to go."

"That then could drive us back towards thinking about a military option to stop the North Koreans from developing a nuclear weapon that could hit the United States. So that's where the gamble is and there's no track record here. Kim Jong Un hasn't met with the Chinese leadership, he's not met with the South Korean leader much less the American leader."