US Secretary of State Hillary Clinton on Tuesday voiced regret that North Korea's new leader Kim Jong-Un has failed to take steps to end the isolation of his people since coming to power.

Addressing a so-called global "townhall" to field questions from Inter-users and global broadcasters, Clinton told audiences the United States was concerned about "what the new regime in North Korea is doing and threatening."

"Let me express my regret, because I think with a new, young leader we all expected something different. We expected him to focus on improving the lives of the North Korean people, not just the elite but everyone," Clinton said.

Instead of providing "more education, more openness, more opportunity," she said Kim "has engaged in very provocative rhetoric and behavior."

She said that she had spent time during her four years in office having "long conversations" with her counterparts in Japan, China and South Korea about Pyongyang "because this is a threat to all of us."

"And it is something that is so regrettable when young people the world over, including in North Korea, are getting better-connected with the rest of the world, to remain as closed off and denied the opportunities they should have," she said.

Kim, who is thought to be in his late 20s, came to power in late 2011 inheriting the world's last communist dynasty after the death of his father, Kim Jong-Il.