"We will continue to press them to meet their international obligations. But we have no new concerns as a result of this event," he said.
Carney declined to make any assessment of the younger Kim. "We will judge the North Korean government as we always have: by its actions," he said.
The administration had been poised to announce a significant donation of food aid to North Korea this week, the first concrete accomplishment after months of behind-the-scenes diplomatic contacts between the two wartime enemies, according to those close to the negotiations. And an agreement by North Korea to suspend its controversial uranium enrichment program was expected to follow within days, the officials said.
Nuland said the U.S. wanted to be respectful of North Korea's period of mourning, and would need to re-engage "at the right moment."
Suspension of uranium enrichment by North Korea had been a key outstanding demand from both the U.S. and South Korea. North Korea has tested two atomic devices in the past five years. Recent food talks in Beijing yielded a breakthrough on uranium enrichment, the sources said.
The officials spoke on condition of anonymity because of the sensitivity of the subject and the sensitivity of dealing with North Korea in general.
The food aid announcement would have not only been welcome news for North Korea, but also pave the way for a crucial U.S.-North Korea meeting in Beijing on Thursday. That meeting in turn could lead to the resumption of nuclear disarmament talks that also would include China, Japan, Russia and South Korea.
The so-called six-party talks were last held three years ago, and resuming them would amount to a foreign policy coup for the Obama administration.
Two senior U.S. diplomats were in North Korea's lone ally, China, last week to discuss the issues. They met Obama's top national security aides on Monday to discuss the way forward. But decisions will be delayed as it is not clear whether North Korean officials will be in position to handle any engagement with the outside, the U.S. officials said.
The top U.S. military officer, Gen. Martin Dempsey, told reporters in Germany the United States and its allies had not seen any change "in North Korean behavior of a nature that would alarm us," according to the American Forces Press Service. The Joint Chiefs of Staff chairman said there had been no changes to the alert readiness for U.S. forces on the peninsula, although South Korea has put its military and police on alert.
Kim's death was announced by state media in a "special broadcast" from Pyongyang late Sunday. North Korea will hold a national mourning period until Dec. 29. Kim's funeral will be held on Dec. 28, it said.