ⓒYONHAP News

Washington is seeking to make sure that inter-Korean relations won't outpace its nuclear negotiations with North Korea.

"We have made clear to the Republic of Korea that we do want to make sure that peace on the peninsula and the denuclearization of North Korea aren’t lagging behind the increase in the amount of inter-relationship between the two Koreas." 

Speaking to reporters on Tuesday, U.S. Secretary of State Mike Pompeo said that's why Seoul and Washington have established a joint working group, which will ensure they don’t talk past each other or take an action that the other is unaware of.

"We view them as tandem, as moving forward together. We view them as important parallel processes... and that working group is designed to make sure they continue to remain that way."

As Pompeo stressed tight coordination, Seoul and Washington held the first meeting of their working group in Washington on Tuesday.

After the meeting, Seoul's chief nuclear negotiator Lee Do-hoon said he and his U.S. counterpart Stephen Biegun discussed denuclearization, UN sanctions, and inter-Korean cooperation.

"I was able to confirm the U.S.' strong support regarding a joint survey related to a South-North rail connection project."

"Our aim is to hold a groundbreaking ceremony within this year."

Following the inter-Korean summit in April, the two Koreas in August sought to run a South Korean train along the length of North Korea to the Chinese border to survey rail conditions. But, the effort was thwarted by the South Korea-based UN Command, which did not approve the crossing of the military demarcation line.

The Unification Ministry official in Seoul said Thursday that the government is in discussions with the U.S. and the UN on how to exempt an inter-Korean railway project from international sanctions.