North Korea proclaimed the beginning of the Kim Jong Un era Thursday, defining the son of its late leader, Kim Jong Il, as “successor of its revolutionary undertakings and leader of its people.”

North Korea's official newspaper Rodong Sinmun said in an editorial Thursday Kim Jong Un should move forward on a path of Juche (self-reliance) and military-first revolutions while keeping the teachings of Kim Jong Il. It urged the nation to rally behind the young leader and faithfully uphold his leadership.

Tens of thousands of North Koreans continue to mourn to death of Kim Jong Il who led the nation for 17 years.

Foreign governments are watching events in Pyongyang closely because of concerns over the younger Kim's rise in a country with a nuclear program, a large army and a history of deep animosity towards its neighbors.

In Seoul, South Korean President Lee Myung-bak urged stability in the North. He told a meeting of political leaders Thursday early stabilization of North Korea's system is “in the interests of neighboring countries.”

He added that Seoul is willing to soften its stance, saying there is room for flexibility in future relations with Pyongyang.

The United States also expressed optimism over the possibility of working with a new North Korean leader. U.S. defense department spokesman John Kirby called on North Korea to end its closed door policy during a press conference at the Pentagon on Wednesday.

“There is an opportunity here for the North Korean regime, whoever heads it. It's an opportunity to join the family of nations, and to stop the isolation that they have suffered their people through, and we certainly hope that they will take that.''

U.S. officials have held several rounds of informal talks with North Korea since June, but it is not clear when the two sides will meet again. The United States has been trying to persuade North Korea to rejoin six-party negotiations in which regional powers have called for Pyongyang to give up its pursuit of nuclear weapons in return for diplomatic and other incentives.

South Korea is also seeking the resumption of six-party talks. South Korea's nuclear envoy traveled to China on Thursday to discuss the aftermath of Mr. Kim's death and ways to move forward with the denuclearization of North Korea.

The talks involve the two Koreas, the United States, China, Japan and Russia, and have been at a standstill since 2008.