U.S. Secretary of State Mike Pompeo said on Sunday that inter-Korean relations are an important factor in North Korea's denuclearization.

Pompeo made the remarks during a telephone interview with a U.S. radio station when asked about a working group recently launched between the U.S. and South Korea. 

He said that inter-Korean relations are moving forward in tandem with U.S.-North Korea negotiations and that Washington and Seoul are keeping in step. 

He also reaffirmed that sanctions against the North will remain in place as they have led the regime to engage in negotiations.