Trump's rhetoric on North Korea 'makes people nervous' but actions are positive: former US envoy

— -- A former U.S. envoy said President Trump's aggressive rhetoric toward North Korea over its nuclear program "makes people nervous," but he praised some of the administration's actions in response to the North Korean threat as encouraging.

Christopher Hill, former U.S. ambassador to the Republic of Korea, told ABC News' Martha Raddatz on “This Week” Sunday that he thinks President Trump "is trying to out-North Korean the North Koreans" with his tough rhetoric.

"Let’s see if that works," Hill said. "Certainly it makes people nervous when they’re not quite sure what he means by it. And, you know, great powers can’t really bluff. So when you talk in those terms, you’ve got to be prepared to back it up. And I guess that’s what worries people the most."

Hill added that he appreciates that President Trump has understood that North Korea’s nuclear program “is a major issue" and that the administration has made encouraging moves, including Vice President Mike Pence's trip to the Asia-Pacific region this weekend. Pence is visiting South Korea, Japan, Indonesia and Australia.

South Korea, which has about 20 million people living within artillery range of North Korea, worries about not being included in two things: U.S. decisions on pre-emptive action against its northern neighbor and U.S. discussions with the Chinese over the issue, Hill told Raddatz, who anchored the show from South Korea.

South Korea “kind of take[s] the view, ‘Look, there shouldn't be anything about us without us,’ and so I think the effort to kind of clue them in, to be close to them, to listen to them, to discuss the strategy, I think is very crucial,” Hill said.

“The days where the U.S. would negotiate with North Korea and leave the South Koreans at the airport wondering what was going on -- those days are over,” he said. “We work very closely with South Korea, and I think in the process [it has] brought the U.S. and South Korea together.”

The former ambassador also called the administration’s discussions with China about North Korea “very encouraging.”

“[Working with the Chinese] seemed to be an elusive concept at a certain point in time and, yet that, I think, is very much happening,” he said.

He added that Trump needs to fill the post Hill previously held as U.S. ambassador to South Korea, saying, "but I guess that takes a long time for this administration."

Hill said the threat from North Korea has increased since the period of 2005 to 2007 when he headed a U.S. delegation to six-party talks aimed at addressing North Korea's nuclear program.

“First of all, they've had over 25 missile tests. They're working on a whole new generation of missiles, and of course one of them failed in the last 24 hours,” he said. “He'll try again. So it's a new generation of missiles.”

He warned that North Korea’s goal with its nuclear program is “more ambitious” than just seeking “regime survival.”

“People often take the view, ‘Well, somehow this is all about their regime survival, this is how they'll survive, being a nuclear-weapons country,” Hill said.

“Actually, I think they're more ambitious about it. They see this as a means to somehow decouple the U.S. from its ally in South Korea, from its ally in Japan, and somehow create a situation whereby, at least in theory... the U.S. would be less willing to participate in a conflict on the Korean peninsula were it to come to that,” he said.