A senior South Korean official says Pyongyang remains ready to conduct a nuclear test at any time, and could do it around the US presidential election in November.

Presidential national security office chief Shin Won-sik talked about the possibility of North Korea's seventh nuclear test during his appearance on a YTN TV news program on Monday.

Shin said North Korea has maintained the ability to conduct a nuclear test whenever leader Kim Jong Un decides. He added that the North still needs more than one test for nuclear miniaturization.

He said Pyongyang will go ahead with a test if it determines the move would give it a strategic advantage.

He said it is highly probable that the North will make such a determination either before or after the US presidential race.

Shin referred to Kim's visit to a uranium enrichment facility revealed by North Korean media earlier this month. He said North Korea is seeking to draw global attention to its nuclear capabilities to increase leverage around the time of the US election.