North Korea notified the United States earlier this week of its decision to restart its nuclear reactor in Yongbyon.

A Seoul official said Thursday that a North Korean working-level official informed U.S. monitors working at Yongbyon Tuesday of Pyongyang's decision to begin rebuilding its reactor. Seoul reportedly received the information from the U.S. the same day.

The official said North Korea had begun to move stored equipment back to its Yongbyon nuclear complex, a move that led the Seoul government to conclude Pyongyang is taking steps to reassemble the facility.

Washington had a different interpretation, although the Seoul official said the difference in views between Seoul and Washington was negligible.

Meanwhile, South Korea’s top envoy to six-party nuclear talks, Kim Sook, will meet his American counterpart Christopher Hill in Beijing Friday for consultations. Kim will reportedly meet with his Chinese counterpart the next day.