Top U.S. nuclear envoy Christopher Hill says when North Korea completes its nuclear disablement, the two Koreas could accelerate cross-border economic cooperation.

In a meeting with Unification Minister Lee Jae-joung in Seoul, Hill stressed, however, that the relevant parties must first focus on the North’s nuclear disablement.

On his planned three-day trip to North Korea slated to begin Monday, Hill said he will discuss Pyongyang's declaration of its nuclear programs after visiting the Yongybon nuclear facilities.

The U.S. envoy added he thinks the denuclearization process should be complete by next year. He said he would also discuss the timeline with North Korean officials during his next trip.