"We need to see where they are and where they go as they move through their transition period," State Department spokeswoman Victoria Nuland said Monday as top Obama administration officials -- including Secretary of State Hillary Clinton and Defense Secretary Leon Panetta -- held urgent talks with their counterparts in South Korea and elsewhere following the death of North Korean leader Kim Jong Il and the announced succession of his untested young son Kim Jong Un.
President Barack Obama spoke with South Korean President Lee Myung-bak late Sunday U.S. time. South Korea had put its military on high alert.
Other administration officials devoted much of Monday to talking with their counterparts in China, Russia and Japan.
The Obama administration pledged to back a "peaceful and stable transition" in North Korea. Similar calls were issued by other world leaders.
China moved to deepen its influence over senior North Korean officials, particularly with those in the military, Chinese and foreign former government officials and analysts told The New York Times and other news organizations.
Joint Chiefs of Staff Chairman Gen. Martin Dempsey said Washington saw no alarming changes in Pyongyang's behavior and made no change in alert readiness for the 28,000 U.S. forces on the Korean peninsula.
Kim Jong Il, 69, died of a heart attack while on a train Saturday, the government said.
Within hours of the announcement, North Korea's ruling Workers Party Monday called on the nation to unite "under the leadership of our comrade Kim Jong Un."
White House spokesman Jay Carney said, "We hope that the new North Korean leadership will take the steps necessary to support peace, prosperity and a better future for the North Korean people."
Concerning food aid, a top U.S. diplomat held talks with North Korea's chief diplomat on U.S. affairs in Beijing Thursday on the possibility of resuming food aid to the country, the State Department said.
Department officials refused to disclose details on the talks -- which in itself broke nearly three years of official silence on the topic -- but said a key issue is to ensure the aid would go to the North Korean public and not to "some leader's banquet table," Nuland said Wednesday.
Washington intended to propose nutrition-rich items that are considered less likely to be diverted to the North Korean elite.
The talks took place between U.S. Special Envoy for North Korean Human Rights Issues Robert King and Ri Gun, who is also North Korea's deputy nuclear negotiator to the so-called six-party talks, seeking to find a peaceful resolution to security concerns over North Korea's nuclear weapons program.
North Korea is the only industrialized economy not able to feed itself, relying instead on emergency international humanitarian relief, USA Today reported.
Pyongyang claims its food problems are caused by the cutoff of aid from the former Soviet bloc and a "hostile" U.S. policy.
Analysts suggest the North's central-planning socialism and massive military spending are to blame.
Kim Jong Un, the youngest son of Kim Jong Il, was born to his third wife or consort Ko Young-hee in either January 1983 or 1984 and was promoted to the Workers Party Central Committee, North Korea's governing Cabinet, in September 2010.
He was educated in Switzerland and is reported to be a fan of NBA basketball, USA Today said. He is also reported to speak English and German.
At the time of the younger Kim's public debut, his father announced appointments for three of his contemporaries -- his sister Kim Kyong Hui, her husband, Jang Song Thaek, and trusted Gen. Ri Yong Ho -- as a kind of protectorate around the son.
His father also proclaimed his son a four-star general and vice chairman of the National Defense Commission, "the highest guiding organ of the military" and the country's most powerful body.
The North's official Korean Central News Agency said Monday the younger Kim would also lead the committee overseeing his father's funeral, set for Dec. 28.
The agency also said foreign delegations would not be invited to the funeral, which The Wall Street Journal said relieved diplomats in Washington, Seoul and Tokyo -- which North Korea portrays as mortal enemies -- of potentially awkward decisions about who to send to Pyongyang.