"We're continuing to assess the event to determine the veracity of the claim made by the North Korean government that they made an underground nuclear test," Pentagon spokesman Bryan Whitman said at a briefing.

"There will be a period of time where more information is being gathered, and at some point we'll know more about this test," he said.

Earlier Tuesday, White House spokesman Tony Snow admitted that it takes time to know whether the DPRK actually tested a nuclear bomb and the United States might never get a conclusive answer.

"This may take some time, it's a complex undertaking. There is a remote possibility that we'll never be able to determine fully," Snow said.

The DPRK claimed Sunday night that it had successfully set off its first nuclear test. However, U.S. intelligence officials have voiced doubt over the claimed nuclear test as the seismic readings were shy of a typical nuclear detonation.