White House press secretary Robert Gibbs pushed North Korea to return to the six-party talks between Pyongyang and the U.S., South Korea, China, Russia and Japan.
Also, State Department spokesman P.J. Crowley said that the administration is reviewing the evidence brought by those American scientists who were privy to the details of the North's uranium enrichment facility.
Crowley described the plant disclosure as a "publicity stunt" and a "show and tell" exercise.
This "show-and-tell from North Korea has potentially serious implications," he said. "I'm not dismissing the potential significance of this. But based on a relatively brief exposure to some technology by itself we can't, you know, draw implications about how mature this capability may be."
Crowley also said U.S. officials are not yet certain what to make of the facility. He said the Obama administration would weigh all available information, before making a decision.
However, critics said the Obama administration's lack of urgency and focus shows a failure to deal with a potentially frightening security threat.
The Associated Press contributed to this report.