A team of US nuclear experts had arrived at Yongbyon, north of Pyongyang, where DPRK's sole functioning nuclear reactor is situated and begun the work of disabling the facilities, deputy State Department spokesman Tom Casey told reporters.

"This is a positive first step in the process and we certainly hope to see it continue," Casey said.

The spokesman provided no details about the process, but said "This is going to be a process that is going to take some time."

The DPRK shut down Yongbyon nuclear reactor in July. It agreed to disable all existing nuclear facilities and to provide a complete and correct declaration of all its nuclear programs by the end of this year, according to a joint document released on Oct. 3 when the second phase of the sixth round of six-party talks ended in Beijing.

The document said the disabling of the five megawatt Experimental Reactor, the Reprocessing Plant (Radiochemical Laboratory) and the Nuclear Fuel Rod Fabrication Facility in Yongbyon would be completed by Dec. 31.

The six-party talks involve the DPRK, the United States, China, South Korea, Japan and Russia.