The highest-ranking North Korean official ever to defect to South Korea has left for the United States for a ten-day visit.

Hwang Jang-yop was invited by a Washington-based think tank, the Defense Forum Foundation. During his stay in the U.S., Hwang will speak about political and human rights situations in his former communist homeland at a forum sponsored by the conservative think tank.

Hwang will also meet Undersecretary of State for Arms Control and International Security John Bolton and Assistant Secretary of State for East Asian and Pacific Affairs James Kelly.

This is Hwang's first overseas trip since his defection to South Korea in 1997.

Hwang formerly served as a secretary of the North Korean Workers' Party and is known as the architect of North Korea's juche, or self-reliance, ruling theory.

Hwang's previous attempts to visit the United States were discouraged because of Seoul's concern that his criticism of Pyongyang could negatively affect inter-Korean relations.