A North Korean government official says his country's nuclear tests will "never stop" as long as the U.S. continues what he describes as "acts of aggression."

Sok Chol-won, director of North Korea's Institute of Human Rights at the Academy of Social Sciences, spoke to CNN Wednesday.

He declined to confirm when Pyongyang may conduct a sixth nuclear test but said the timing would not be influenced by outside events.

He said nuclear testing is an important part of his country's continued efforts to strengthen what the North has long described as a deterrent to U.S. aggression.